Category: Chemistry
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Discovery of Protons: Model, Discovery, and Experiment
Continue ReadingWhat are Protons?
The three different sub-atomic particles present in the nuclei of an atom are called, protons, neutrons, and electrons and they were discovered in the nineteenth and twentieth century.
Discovery of Protons
The nucleus of the atom was discovered by a scientist named Ernest Rutherford in the year 1911 in his well-known gold foil experiment. He stated that all the positively charged particles present in an atom were concentrated in a singular core and that maximum of the atom’s volume was empty.
He also stated that the total number of positively charged particles present in the nucleus of an atom is always equal to the total number of negatively charged electrons present around it.
The finding of the proton is credited to Ernest Rutherford, who showed that the nucleus of the hydrogen atom (that is a proton) is present in the nuclei of all atoms in the year 1917. But, the presence of a positively charged particle found in an atom had been first noticed by E. Goldstein in the year 1886 based on the concept that atoms are generally electrically neutral which means that they have the same number of positive and negative charges.
He performed a series of experiments and detected that when high voltage electricity was passed through a cathode tube which was fitted with a perforated cathode (pierced disk) and thus contained gas at low pressure then a new type of ray was produced from a positive electrode or commonly called as the anode which moved towards the cathode.
These new rays he named as canal rays, positive rays, or anode rays. Further, the canal Ray experiment is the experiment that was performed by German scientist Eugen Goldsteinin that led to the discovery of the proton. The discovery of proton occurred after the discovery of the electron which further supported the structure of the atom.
The Canal Ray Experiment
• The apparatus as shown above in the figure is set by providing a very high voltage source and emptying the air to preserve low pressure inside the tube.
• High voltage is thus passed to the two metal pieces as shown to ionize the air and hence making it a conductor of electricity.
• The electricity started to flow as the circuit completes.
• When the voltage was increased further to several thousand volts, then a faint luminous ray was observed extending from the holes in the back of the cathode.
• The rays thus observed were moving in the opposite direction of cathode rays and were termed as canal rays.
Conclusion of Canal Ray Experiments
• As compared to cathode rays, canal rays depend upon the nature of gas present in that tube. It is because of the fact that the canal rays consisted of positive ionized ions which were formed by the ionization of gas present in the tube.
• The behavior of particles present in an electric and magnetic field was thus the opposite to that of cathode rays.
Protons Characteristic
Protons are referred to as the positively charged subatomic particles of an atom. It is represented by the symbol p or p+.
A hydrogen atom comprises of one proton and one electron, so when an electron is removed from the hydrogen atom then a proton is produced. This is the reason why the proton is also represented as H+.
It thus possesses +1e (or 1.60 10-19 coulomb) positive electric charge.
The word Proton is a Greek word that means ‘First’. It was initially used by Ernest Rutherford in the year 1920. The subatomic particles protons and neutrons are collectively known as nucleons.
What is The Mass of Protons?
The mass of the proton is 1.67 10-24 gram or 1.67 10-27 kg.
The mass of an electron is equal to 9.1 10-28 consequently the mass of a proton is 1836 times the mass of an electron. Though the mass of a proton is almost always equal to the mass of a neutron present in the nuclei of an atom.
The number of protons present inside the nucleus of an atom is always equal to the atomic number (Z) of the atom.
Mathematically,
Number of Protons = Atomic Number
For instance, the atomic number of the Krypton (Kr) atom is equal to 36. Henceforth, the nucleus of the Krypton atom consists of 36 protons.
Properties of Protons / Positive Rays / Anode Rays
1. They are positively charged ions.
2. They travel in straight lines and thus can cast a shadow of the thing located in their path.
3. These positive rays are also deflected by electric as well as a magnetic field.
4. Mass of proton is equal to 1.672 x 10-24 g.
5. The charge on the proton is equal to +1.602 x 10-19 coulombs.
Protons Citations
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Discovery of Neutrons: Model, Discovery, and Experiment
Continue ReadingWhat are Neutrons?
Neutrons are referred to as subatomic particles that are one of the main constituents of atomic nuclei.
Neutrons are generally denoted by the symbol n or no.
Neutrons do not have any net electric charge linked to them. They do, though, have a mass that is slightly greater in magnitude as compared to a proton.
Neutrons and protons are together referred to as nucleons since they usually behave similarly.
The mass of a neutron can be nearly approximated to one atomic mass unit or amu.
Nuclear physics is the branch of science that deals with the study of the properties of neutrons and the relations of these subatomic particles with other substances.
The complete nuclear and chemical properties of an element are generally determined by the total number of protons present in its atomic nucleus (atomic number) and the total number of neutrons present in its respective atomic nucleus or it is also referred to as the neutron number.
The sum of the total number of protons present in a nucleus of a given atom and the total number of neutrons in the atomic nucleus gives the mass number of that atomic nucleus.
The protons and the neutrons present inside the nucleus of an atom are bound together through nuclear forces.
For the stability of atomic nuclei, the existence of neutrons is essential. The only exception to the above-mentioned rule is the nucleus of protium or hydrogen-1.
Discovery of Neutrons
Neutrons were initially hypothesized by the New Zealand-born British physicist named Ernest Rutherford in the year 1920.
But, the discovery of neutrons is credited to the British physicist named James Chadwick in the year 1932. He was also awarded the Nobel prize in physics for this finding in the year 1935.
During the year the 1920s, the common hypothesis on the nature of atoms was that they comprised of protons and also nuclear particles called electrons. Though, this failed to obey the Heisenberg uncertainty principle in quantum mechanics.
Consequently, in the year 1931, two German nuclear physicists noticed that when the alpha particle radiation that is emitted by polonium is made incident on beryllium, lithium, or boron, it then resulted in the production of a strangely penetrating form of radiation.
Further, it was confirmed by James Chadwick through a series of trials that these particles that constituted the strangely penetrating radiation were called neutrons.
James Chadwick fired alpha radiation at the beryllium sheet from a polonium source which led to the creation of uncharged, penetrating radiation.
This uncharged, penetrating radiation was thus made incident on paraffin wax, a hydrocarbon having a fairly high hydrogen content.
The protons that were ejected from the paraffin wax were noticed with the help of an ionization chamber.
This range of the liberated protons was measured and the contact between this uncharged radiation and the atoms of numerous gases was studied by James Chadwick.
He, at last, concluded that the oddly penetrating radiation thus comprised of uncharged particles having (roughly) the same mass as that of a proton.
These particles were later called ‘neutrons’. The total number of protons and neutrons present in the nucleus of an atom indicates the mass number of that particular atom.
Mathematically,
Mass Number = (Number of Protons) + (Number of Neutrons)
Charge and Mass of Neutrons
The electric charge thus associated with a neutron is equal to 0. Hence, neutrons are neutrally charged subatomic particles.
The mass of a neutron is nearly equal to 1.008 atomic mass units.
Subsequently, the subatomic particles named as neutrons lack an electric charge, so their mass cannot be directly determined through the analytical technique of mass spectrometry.
Properties of Neutrons
Even though the neutron is considered to be a neutral particle, the magnetic moment of these particles (neutrons) is not equal to zero.
Even though electric fields have majorly no effect on neutrons, these subatomic particles are still affected by the presence of magnetic fields.
The magnetic moment related to the neutron can be considered as a sign of its quark organization or structure and the distribution of its internal charges.
The mass of neutrons is always equal to that of protons present inside the nucleus of an atom (Mass of the neutron is 1.675 x 10-24g).
The density of neutron is equal to 1.5 x 1014 g/cc.
Applications of Neutrons
In various nuclear reactions, the subatomic particle named as the neutron plays an important role.
Information about neutrons and their activity has been especially vital in the past for the expansion of many nuclear reactors and numerous nuclear weapons.
The nuclear fissioning of some elements such as uranium-235 and plutonium-239 is almost always triggered by their neutron absorption.
Warm, cold, and hot neutron radiation plays a very significant application in neutron scattering facilities where the radiation is often used in condensed matter research with the support of X-rays.
One of the most important applications of neutrons includes the excitation of delayed and triggered gamma rays from material components. This also forms the basis for the study of neutron activation analysis, frequently abbreviated to NAA.
NAA is most commonly used to examine the small samples of materials present inside a nuclear reactor.
Neutrons Citations
- Neutrons from high-energy x-ray medical accelerators: an estimate of risk to the radiotherapy patient. Med Phys . May-Jun 1984;11(3):231-41.
- Neutrons in active proton therapy: Parameterization of dose and dose equivalent. Z Med Phys . 2017 Jun;27(2):113-123.
- The potential and limitations of neutrons, electrons and X-rays for atomic resolution microscopy of unstained biological molecules. Q Rev Biophys . 1995 May;28(2):171-93.
- Neutrons are forever! Historical perspectives. Int J Radiat Biol . 2019 Jul;95(7):957-984.
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Bohr Model of Atom: Definition, Diagram, Example
Continue ReadingWhat is Bohr Model?
o The Bohr model was an improved form of earlier cubic model (1902), the plum-pudding model (1904), the Saturnian model (1904), and the Rutherford model.
o The Bohr model is sometimes also referred to as the Rutherford-Bohr model.
o Bohr combined Planck’s and Einstein’s quantization ideas into a model of the hydrogen atom that set the contradiction of atom stability and discrete spectra.
o The Bohr model of the hydrogen atom elucidates the connection between the quantization of photons and the quantized emission from the atoms.
o Bohr described the hydrogen atom in terms of an electron that moves in a circular orbit around a nucleus.
o He hypothesized that the electron was thus limited to certain orbits termed as discrete energy levels.
o Electrons can also jump between these orbits either by absorbing or releasing photons.
o When an electron travels from a higher-energy orbit to a more stable orbit, energy is emitted in the form of a photon. And when an electron jumps from a stable orbit to a more excited orbit, a photon of energy is absorbed.
o Hence, by using the Bohr model, we can analyse the energy of an electron and the radius of its orbit in any one-electron system.
Characteristic of Bohr Model
o The Bohr model represents that the electrons present in any atom revolve in orbits of different energy around the nucleus just like planet revolve around the sun.
o The term energy levels (or shells) are used to define these orbits of differing energy. He stated that the energy of an electron is quantized, which means electrons can move from one energy level to another but there is nothing in between.
o The energy level that is occupied by an electron is called its ground state. But by absorbing energy it can thus move to a higher-energy, less-stable level, or shell. This higher-energy, or less-stable state is termed as excited state of the electron.
o The electron can also return to its original, stable ground state by releasing the energy it has absorbed, as shown in the figure below.
Bohr Model of Atom
Ground and Excited States of Electron
o Bohr stated that an electron needs less energy if it close to the nucleus, but as it moves away from nucleus it needs more amount of energy.
o The frequency of the photon of light thus emitted depends upon the variance of two energy levels.
E2-E1 = hv
Where E2 is defined as the energy of higher level and E1 is defined as the energy of lower level and h is termed as Planck’s Constant.
o So, Bohr numbered the different energy levels or shells. These are numbered as 1,2,3,4…or K, L, M, N…. shells preliminary from the shell near to nucleus.
o Bohr also found that the numerous energy levels can occupy only a fixed number of electrons for instance; energy level 1 or K shell can accommodate only 2 electrons, energy level 2 or L shell has 8 electrons, and so on.
o Number in various shell is determined by the formula – 2n2 where n is defined as number of shells assigned to various energy shell of an atom.
Bohr Model of Atom
Merits of Bohr model
o The Bohr model was the foremost model to postulate the quantization of electron orbits in atoms. Thus, it indicates an early quantum theory that also gave a way to development of modern quantum theory. It presented the concept of a quantum number to define the atomic states of any atom.
o Bohr described the stability of atoms. He stated that an electron does not radiate energy if it is present in the same shell.
o He explained the spectrum of hydrogen and he also calculated the size of atom was accurately. The drawback of Rutherford model of atom was that the atoms become unstable when accelerated charge, radiated energy, and lastly fell into nucleus. This theory of Rutherford was thus eliminated.
Limitations of Bohr Model
o The Bohr atomic model theory explains that electrons of any atom have both a known radius and an orbit that is, fixed position and momentum at the same time, which is nearly impossible according to Heisenberg Uncertainty Principle.
o The Bohr atomic model theory properly explained the structure of small sized atoms for instance – hydrogen, but for larger atoms poor spectral predictions are obtained. Hence, it could not explain the structure of large sized atoms.
o The Zeeman effect could not be explained by Bohr which states that the spectral line generally splits into several components in the presence of a magnetic field.
o The Stark effect could not be explained by Bohr, which states that the spectral line generally splits into fine lines in the presence of an electric field.
o Bohr model cannot predict the relative intensities of several spectral lines.
Bohr Model Citations
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What are Isobars? Definition, Types, and Examples
Continue ReadingWhat are Isobars?
o Isobar is defined as the element which varies in their chemical property but has the same physical property.
o Consequently, it can be said that isobars are those elements which have a different atomic number and same mass number or nucleon number.
o Their chemical property differs because of the difference in the number of electrons that are present in their respective nuclei.
o The sum of the number of protons and neutrons together form the atomic mass of an element.
Atomic Mass = Protons +Neutrons
Protons and neutrons are together known as nucleons. Hence, it can be said that the number of nucleons that are present in the nucleus of an atom is always equal to the atomic mass of that atom. Thus, it will have the same number of nucleons.
o Isobars always have different atomic structure because of the difference in their respective atomic numbers.
o The number of neutrons present in a nucleus of an atom makes up the difference in the number of nucleons. Thus, isobar always have different chemical properties.
Isobars Examples
o The isobars iron and nickel. Iron and nickel have different atomic number 26 and 28 respectively. However, they have same mass number that is 58.
o Another example of isobars include; argon and calcium with different atomic numbers 18 and 20, respectively. But they have the same atomic mass that is 40.
o Moreover, sometimes there are series of an element that has same atomic mass.
o For instance, Cobalt (Co), Nickel (Ni), Copper (Cu), and Iron (Fe) have same atomic mass 64 but the atomic number of each differs.
oSome more examples are;
o 18Ar40 19K40 20Ca40 have same mass number 40, but different atomic number.
o 32Ce76, 34Se76 have same mass number 76, but different atomic number.
o 11Na24 12Mg24 have same mass number 24, but different atomic number.
o 26Fe58, 27Ni58 have same mass number 58, but different atomic number.
o 27Co64 28Ni64 have same mass number 64, but different atomic number.
Isotopes
o Atoms are made up of electrons, protons, and neutrons.
o The nucleus of an atom is made up of protons and neutrons and the electrons revolve around the nucleus.
o Isotopes are referred to as the atoms in which the number of neutrons varies and the number of protons is the same.
o From the above definition, it can be concluded that isotopes are defined as those elements that have the same atomic number and different mass number.
o For instance – isotopes of hydrogen: There are three isotopes of hydrogen and these are named as protium, deuterium, and tritium. All three of them that are mentioned above have the same number of protons, but the numbers of neutrons vary. In protium the number of neutrons is equal to zero, in deuterium, number of neutrons is equal to it is one and lastly in tritium, the number of neutrons is two.
Isotopes vs Isobars
Isobars Isotopes Isobars are referred to the atoms of different chemical elements having same atomic mass. Isotopes are referred to as the atoms with the same number of protons but different numbers of neutrons. The atomic masses are equal. The atomic masses vary. The physical properties are similar. Physical properties are different. Atomic numbers of elements are different. Atomic numbers of elements are the same. For Instances: 11Na24 12Mg24 Have same mass number 24, but different atomic number. For Instance:- Isotopes of Hydrogen- There are three isotopes of hydrogen and these are named as protium, deuterium, and tritium. Uses of Isobars
o Nuclear reactors may use the uranium’s isobars.
o Iodine’s Isobars are generally used in treatment of goitre.
o For cancer treatment, isobars of cobalt are usually used.
Isobars Citations
- Differentiation of hydroxyproline isomers and isobars in peptides by tandem mass spectrometry. Anal Chem . 1990 Aug 1;62(15):1691-5.
- Isobars, the coexistence curve, and the critical exponent β of N-isopropylacrylamide gels obtained using a simple experimental method. Phys Rev E Stat Nonlin Soft Matter Phys . 2013 Feb;87(2):022603.
- Unique Structural/Stereo-Isomer and Isobar Analysis of Novel Fentanyl Analogues in Postmortem and DUID Whole Blood by UHPLC-MS-MS. J Anal Toxicol . 2019 Oct 17;43(9):673-687.
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Cathode: Definition, Examples, and Anode vs Cathode
Continue ReadingWhat is Cathode?
o The terms Cathode and Anode were confirmed in 1834 by a scientist named William Whewell. He derived the words from the Greek word, kathodos which means ‘way down’ In simple words, an electrode is defined as a substance that helps in the conduction of electricity where the electric current either arrives or leaves the non-metallic medium like an electrolytic cell.
Electrode
o An electrode is referred to as the vital component of an electrochemical cell that makes contact with an electrolyte.
o Electrode usually acts as a metallic contact from which the current enters and leaves the electrolyte.
o More precisely, it can be said that the electrode provides a surface where a redox reaction generally takes place between the metal and the solution.
Types of Electrode
Electrodes comprise of;
i. Cathode
ii. Anode
Cathode Characteristic
o Cathode and anode are both defined by the flow of current. Consequently, a cathode is an electrode from which the current leaves a polarized electrical device.
o Similarly, an anode is an electrode from which a current generally enters into a polarized electrical device.
o Further, a cathode is also said to be either a hot cathode or a cold cathode.
o A cathode is heated in the presence of a filament to produce electrons by thermionic emission is commonly known as a hot cathode however cold cathodes are not heated by any filament.
o A cathode is generally labeled as cold if it emits more electrons than the ones produced by thermionic emission alone.
o In the most simple terms, an anode in electrochemistry is referred to the point where an oxidation reaction occurs.
o Commonly, at an anode, negative ions or anions because of their electrical potential tend to react or give off electrons.
Flow of Current
o In simple words, the current is referred to any movement of electrical charge.
o Current generally flows in the same direction as it flows in positive charge carriers.
o The cathode is the negatively charged electrode.
o Few points of the cathode are mentioned below;
o The cathode always attracts cations or positive charges.
o The cathode is the source of electrons or also called an electron accepter and can cause reduction to occur. It may take a positive charge.
o Because the cathode producess electrons, which naturally are the electrical species, it can also be said that cathodes produce charge or that the current flows from the cathode to the anode.
Anode vs Cathode
Some important differences between cathode and anode are mentioned below;
Anode Cathode The anode is defined as the electrode where electricity moves into. The cathode is defined as the electrode where electricity is given out or flows out of. The anode is generally the positive side. A cathode is always the negative side. It acts as an electron donor. It acts as an electron acceptor. In an electrolytic cell, an oxidation reaction usually takes place at the anode. In an electrolytic cell, a reduction reaction usually takes place at the cathode. In galvanic cells, an anode can also become a cathode. In galvanic cells, a cathode can also become an anode Cathode Citations
- Effect of anode-cathode configuration on paresthesia coverage in spinal cord stimulation. Neurosurgery . 1997 Sep;41(3):654-9; discussion 659-60.
- Anode and cathode materials characterization for a microbial fuel cell in half cell configuration. Water Sci Technol . 2011;63(10):2457-61.
- Investigations on the Fundamental Process of Cathode Electrolyte Interphase Formation and Evolution of High-Voltage Cathodes. ACS Appl Mater Interfaces . 2020 Jan 15;12(2):2319-2326.
- Revealing the role of the cathode-electrolyte interface on solid-state batteries. Nat Mater . 2021 May 20.
- Cathode performance as a factor in electricity generation in microbial fuel cells. Environ Sci Technol . 2004 Sep 15;38(18):4900-4.
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Chemical Reaction in Solution: Definition, Types, and...
Continue ReadingWhat is Chemical Reaction?
o Chemical reaction, a process in which one or more substances, the reactants, are converted to one or more different substances, the products.
Type of Chemical Reactions
There are three types of reaction that occurs in solution;
I. Precipitation reaction
II. Acid-base reaction
III. Oxidation-reduction reaction
I. Precipitation Reaction
o This reaction takes place when two aqueous reactants, one solid and one liquid, react to form an insoluble product. This insoluble substance is termed as a precipitate.
o For instance; lead nitrate is mixed with potassium to produce the following compounds as shown in the following chemical reaction:
Pb (NO3)2 + 2KI → PbI2 (ppt) + 2KNO3
o Lead iodide formed here is an insoluble product and hence is titled as a precipitate. Another example for the same include;
AgNO3(aq) + K2Cr2O7(aq) → Ag2Cr2O7(ppt) + KNO3(aq)
o A reddish precipitate of silver dichromate is formed in the above reaction. These reactions shown above are also termed as Double-displacement reactions.
II. Acid-Base reaction
o Arrhenius stated that an acid is defined as a substance that dissolves in water to produce H+ ions, for instance, HCl whereas a base is a substance that dissolves in water to produce hydroxide (OH−) ions.
o When an acid reacts with base in their solution form, they produce salt and water.
o These reactions are also named as Neutralization reactions.
The chemical reaction below shows some of the examples of acid-base reactions;
H2SO4 + Ca(OH)2 → CaSO4 + H2O
H2SO4 + CaO → CaSO4 + H2O
HF + H2O → F– + H3O+
HBr + NH3 → Br– + NH4+
III. Oxidation Reduction Reaction
o Oxidation is defined as a process in which a chemical substance loses electrons during a reaction whereas Reduction is the totally opposite process in which a substance gains electrons or gain hydrogen during a reaction.
o If in a reaction the total number of electrons lost is equal to the total number of electrons gained then these types of reactions are known as Redox reactions.
o The figure given below describes the redox reaction with an example;
Reduction: Removal of Oxygen from CuO
Oxidation: Addition of Oxygen in H2
CuO + H2 → Cu + H2O
Reduction: Removal of Oxygen from Fe3O4
Oxidation: Addition of Oxygen in H2
Fe3O4 + 4H2 → 3Fe + 4H2O
Types of Redox Reactions
o There are a few important types of redox reactions that are mentioned below;
o Synthesis Reactions: The formation of any compound straight from the elements in a redox reaction is known as synthesis reaction, for instance, the formation of water from hydrogen and oxygen as given below:
2H2(g)+O2(g) → 2H2O(g)
o Decomposition Reactions: The decomposition of a compound into its elements is also defined as a type of as redox reaction for instance; the electrolysis of water:
2H2O(l) → 2H2(g)+O2(g)
o Combustion Reactions: It is a kind of redox reaction which occurs between molecular oxygen and compound (reactants) to produce oxygen-containing products. For example;
CH4(g)+2O2(g) → CO2(g)+2H2O
Solution
o A solution is a type of homogeneous mixture in which substances that are present in lesser amounts are called solutes dispersed uniformly throughout the substance present in the greater amount, the solvent.
Types of Solution
o The solution can be of two types as mentioned below;
o Aqueous Solution
o A Non-aqueous Solution
o An aqueous solution is commonly defined as a solution in which the solvent is water, whereas, in a non-aqueous solution, the solvent is not water.
Examples of non-aqueous solvents include ethyl acetate, turpentine, etc.
Why Most Reaction Occur in Aqueous Solution
o For a chemical reaction to occur, individual atoms, molecules, or ions must collide thus, collisions between solids, do not occur at a visible rate.
o It is easy to control the amount of heat used or produced in a reaction when it occurs in an aqueous solution.
o The nature of the reaction can also be controlled when the proper solvent is chosen.
o All the chemical reaction that occurs in our body are possible only in aqueous solution.
o For instance; reaction involved in the digestion of food.
o When an element dissolves in water, it is represented by writing (aq) after its chemical name.
o Hydrophilic or Water-loving substances dissolve in water.
o For instance, when sodium chloride dissolves in water, dissociates into Na+(aq) and Cl– (aq).
o Hydrophobic or water-fearing substances normally do not dissolve in water or form aqueous solutions.
o Example for the same include mixing oil and water which will not result in any dissociation.
Solubility in Water
o Water has some unique properties and is available on Earth in a huge amount.
o Water is also called as a Universal solvent.
o The water molecule comprises of two hydrogen atoms bonded covalently to an oxygen atom in a V-shaped structure.
o The oxygen atom attracts electrons more strongly as compared to the hydrogen atom. It means that the oxygen and hydrogen nuclei do not share equal electrons.
o Hydrogen atoms are generally electron-poor and attain a partial positive charge, which is shown by δ+ whereas the oxygen atom, is more electron-rich, so it attains a partial negative charge.
o This above-mentioned charge is twice as large as the partial positive charge on each hydrogen as the molecule of water has a net zero charge. So, its charge is indicated by 2δ−.
o This unequal distribution of charge forms a polarity in the individual water molecules. Because of this arrangement of a water molecule, it is termed as a polar substance.
o The unequal distribution of charge in polar liquids such as water makes them good solvents for different ionic compounds.
o When ionic solid dissolves in water, the ions present dissociates into cation and anion. The partially negatively charged oxygen atoms of the H2O molecules surround the cations and the partially positively charged hydrogen atoms in H2O surround the anions.
o The arrangement in which cations and anions are surrounded by polar water molecules is termed as hydrated ions.
o Example for the same include; common salt in water.
Chemical Reaction Citations
- Understanding chemical reaction mechanisms in ionic liquids: successes and challenges. Chem Soc Rev . 2011 Jan;40(1):272-90.
- Chemical reactions which affect the biological activity of human gonadotrophins. Biochem J. 1961 Apr; 79(1): 64–70.
- Seeding chemical reactions by focusing. J Chem Phys . 2013 Apr 14;138(14):144502.
- Application of chemical reaction engineering principles to ‘body-on-a-chip’ systems. AIChE J . 2018 Dec;64(12):4351-4360.
- Chemical reactions. Am J Med Technol . 1948 May;14(3):142-6.
- Classification of chemical reactions and chemoinformatic processing of enzymatic transformations. Methods Mol Biol . 2011;672:325-40.
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Molar Mass: Definition, Calculation, and Examples
Continue ReadingWhat is Molar Mass?
Molecules and atoms are very minute, both in size and mass.
The molar mass is defined as the weight of one sample mole.
Relative molar mass is referred to as the smallest mass unit of a compound of one-twelfth of the mass of one carbon – 12 atoms.
The amount of entities present in a particular substance such as atoms, molecules, ions, is defined as a mole.
A mole of any substance is written as 6.022×1023 molecules.
The molar mass of a substance which is also known as the molecular weight is defined as the sum of the total mass in grams of all the atoms that make up a mole of a particular molecule.
The unit of this quantity is expressed in grams per mole.
How to Find the Molar Mass for Compounds?
Compounds are defined as substances that are made up of more than one element. For instance, some general compounds include salt, glucose and acetic acid (or vinegar), etc.
For instance; the compound sodium chloride comprises of two elements which are, sodium and chlorine.
Molar Mass Formula
The molar mass of a compound is defined as the mass of an assumed substance divided by the quantity of substance present in the sample.
Molar Mass = Mass of given substance/amount of substance
The molar mass is an intensive property of the matter and it doesn’t depend upon the dimensions of the sample.
The SI unit of molar mass is kg/mol. Though, for ancient reasons molar masses are almost always expressed in g/mol.
Atomic Mass
The meaning of atomic mass, the mole, and molar mass are all directly or indirectly connected to carbon-12.
This results in two important facts mentioned below;
• The atomic mass of one atom of carbon-12 is precisely 12 atomic mass units or amu.
• The mass of one mole of carbon-12 atoms is also precisely 12 grams and its molar mass is accurately 12 grams per mole.
NOTE: The atomic mass and the molar mass of carbon-12 are statistically equal. They only differ only in SI units; atomic mass is commonly measured in atomic mass units, and molar mass is generally measured in grams per mole.
Mole Definition
In chemistry, the mole is a fundamental (SI) unit used to measure the amount of substance. This quantity is sometimes referred to as the chemical amount. A substance is something that has mass and occupies space.
The molar mass / molecular weight is truly the sum of the total mass in grams of the atoms present to make up a molecule per mole. The unit of molar mass is grams/mole.
How to Determine Molar Mass of a Compound?
To find the molar mass of NaOH.
In a given compound of NaOH, the molar mass of Na is equal to 23 g/mol, the molar mass of O is equal to 16 g/mol, and the molar mass of H is 1 g/mol.
Na+O+H = NaOH
23 g/mol+16 g/mol+1 g/mol= 40 g/mol
The molar mass of the given compound of NaOH is equal to 40 g/mol.
Molar Mass Calculation
The molar mass of a compound is frequently calculated by adding the quantity of atomic masses (in g/mol) of the given constituent atoms.
The property of the molar mass of a given component is just the mass in g/mol.
Though, molar mass also can be calculated by multiplying the mass expressed in amu by the molar mass constant.
For instance; Find the molar mass of hydrogen (H2), sulfur (S8) by using the Molar Mass Formula.
The molar mass of molecules of those elements is always equal to the molar mass of the given atoms multiplied by the number of atoms present in each molecule.
Hence,
Molar Mass of (H2) is equal to 2 × 1.00797(7) × 1.000000 g/mol = 2.01588(14) g/mol
Molar Mass (S8) is equal to 8 × 32.065(5) × 1.000000 g/mol = 256.52(4) g/mol
Molar Mass Citations
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Mole Concept: Definition, Calculation, and Examples
Continue ReadingWhat is Mole Concept
The mole concept is an appropriate method of expressing the amount of a substance.
Any measurement can be fragmented down into two parts – the numerical magnitude and the units that the magnitude given is stated in. For instance, the mass of a ball was measured to be 5 kilograms, the magnitude of this is ‘5’, and the unit is expressed in ‘kilogram’.
What is Mole?
The word “mole” was announced by the German chemist Wilhelm Ostwald in 1896, who derived this term from the Latin word moles that means a ‘heap’ or ‘pile.
In the arena of chemistry, a mole is defined as the amount of a substance that contains precisely 6.02214076 * 1023 ‘elementary entities’ of the given element.
The number 6.02214076*1023 is generally known as the Avogadro constant and is frequently represented by the symbol ‘NA’.
The elementary entities can be characterized in atoms, molecules, monoatomic/polyatomic ions, and other particles like electrons.
For example, one mole of a pure carbon-12 (12C) model will have a mass of precisely 12 grams and comprises of 6.02214076*1023 (NA) quantity of 12C atoms.
The number of moles of a substance in a given example can be denoted by the formula given below:
n = N/NA
n is defined as the number of moles of the substance (or elementary entity)
N is defined as the total number of elementary entities present in the sample,
NA is defined as the Avogadro constant.
The uniqueness of a substance is defined not only by the types of atoms or ions it comprises but by the quantity of each type of atom or ion.
For instance, water, H2O, and hydrogen peroxide, H2O2, are identical in their respective molecules as they both are composed of hydrogen and oxygen atoms. But a hydrogen peroxide molecule encompasses two oxygen atoms, contrasting to the water molecule, which contains only one oxygen atom, the two substances show distinct properties.
The mole offers a link between an easily measured macroscopic property such as bulk or mass, and enormously essential property, the number of atoms, molecules, and so on.
Atomic Mass and Molecular Mass
The atomic mass of an element is defined as the mass of one atom of the element that is expressed in atomic mass units (amu).
It accounts for plenty of the numerous isotopes of the element and allocates an average value to the mass of one atom of the given element.
The atomic mass of a carbon-12 atom is 12 atomic mass units or amu, whereas the atomic mass of a carbon-13 atom is 13 atomic mass units or amu.
The atomic mass of an element is crudely equal to the sum of all the protons and neutrons present in the nucleus of a given atom.
The molecular mass of an element is defined as the sum of the atomic masses of all the components present in an element.
This quantity is also denoted in terms of atomic mass units. Hence, the molecular mass of water is always equal to the sum of all the atomic masses of its constituents present which are hydrogen and oxygen.
The atomic mass of hydrogen is equal to 1.00794 amu and the atomic mass of oxygen is equal to 15.9994 or 16 amu.
Since water molecules comprise of 2 hydrogen atoms and only one oxygen atom thus, the molecular mass of H2O will be 18.0154 amu.
Molar Mass
The molar mass of a given substance is the total mass of one mole of that substance.
It is denoted in terms of ‘grams per mole (g/mol). Though, the SI unit of the above-mentioned quantity is kg/mol. Molar mass can be represented by the formula written below:
The molar mass of a Substance = (Mass of the Substance in grams)/(Number of Moles)
Gram Atomic Mass vs Gram Molecular Mass
The gram atomic mass of an element is defined as the mass of one mole of a specific element. Correspondingly, the gram molecular mass of a compound is defined as the mass of a single mole of a particular compound. Hence, the gram atomic mass of hydrogen is roughly around 1.007g and the gram molecular mass of water or H2O is nearly around 18.015g.
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Scientific Notation: Definition, Calculation, and Examples
Continue ReadingWhat is Scientific Notation?
Scientific notation is a more appropriate way of writing small or very huge numbers.
The scientific notation helps us to signify the numbers which are very huge or very small in a form of multiplication of single-digit numbers and 10 raised to the power of the particular exponent.
The exponent is positive if the number given is very large and it is negative if the given number is very small.
Scientific Notation Representation
The representation of scientific notation is given below;
a × 10b ; 1 ≤ a < 10
To express a number in scientific notation, move the decimal place to the right if the number given is less than zero or to the left if the given number is greater than zero.
For instance, in 456000, in this number the decimal present is after the last zero, therefore to express this in scientific notation, move the decimal to in between the numbers 4 and 5.
The decimal would move five places to the left to get 4.56 as per the representation of scientific notation mentioned above.
The number of times we move the decimal place develops the integer “b.” In the above-mentioned number, the decimal moved five times.
Therefore, the given number in scientific notation would be;4.56 × 105
Scientific Notation Examples
Few Examples of scientific notation are given below;
1. 0.0007 = 7 x 10-4
2. 0.0345 = 3.45 x 10-2
3. 1234000 = 1.234 x 106
4. 8000 = 8 x 103
Another way used to write this expression, is to use the alphabet E which represents “times ten to the power of.”
For instance:
Scientific notation for Avogadro’s number is also an example of scientific notation as shown above on a calculator. 6.02E23 which is the same as6.02 x 1023. This method is mostly used by computer programs and calculators.
Scientific notation enables us to compare between orders of magnitude given in the question.
For instance, 100000000 can be inscribed as 108 in scientific notation. the exponent here is positive. Likewise, 0.0000001 is a very small number and can be represented in scientific notation as 10-8, here the exponent written is negative.
Scientific Notation in Daily Life
Few examples of measurements where the scientific notation is useful are given below;
• The wavelength for violet light is 40-millionths centimeter which can be written in scientific notation as 4 × 10−5cm.
• Some black holes are measured by the number of solar masses they comprise. One black hole measured as 10,000,000 or in scientific notation as1.0 × 107 solar masses.
• A computer hard disk holds 4 gigabytes (about 4,000,000,000 bytes) of data. That is written in scientific notation as 4.0 × 109 bytes.
• Computer calculation speeds are frequently measured in nanoseconds. A nanosecond is equal to 0.000000001 seconds or can be written in scientific notation as 1.0 × 10−9 seconds.
Rules for Scientific Notation
To determine the power or exponent of 10, the following rules must be followed:
• The base must be 10
• The exponent should be a non-zero integer, which means it can be either be written in positive or negative integer
• The absolute value of the coefficient is either bigger than or equal to 1 nonetheless it should be less than 10.
• Coefficients can either be positive or negative figures including whole and decimal numbers.
Positive and Negative Exponent of Scientific Notation
When the scientific notation of any huge numbers is stated, then use the positive exponents for base 10.
For instance: 80000 = 8 x 104, where 4 is expressed as the positive exponent.
When the scientific notation of any small numbers is stated, then the use of negative exponents is used for base 10.
For instance: 0.0006 = 6 x 10-4, where -4 is expressed as the negative exponent.
In simple terms, it can be said that the number larger than 1 can be written as the expression with a positive exponent, while the numbers which are less than 1 can be expressed with a negative exponent.
Scientific Notation Question
Question 1: Convert 0.00000089 into scientific notation.
Solution: We have to move the decimal point to the right of the number 0.00000089 up to 7 places.
The decimal point thus moved 7 places to the right to form figure 8.9
Since the numbers given are less than 10 and the decimal is thus moved to its right.
Therefore, a negative exponent is used here.
⇒ 0.00000089 = 8.9 × 10-7
The above mentioned number is thus written in scientific notation.
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Percentage Composition: Definition, Calculation, and Types
Continue ReadingWhat is Percentage Composition?
The percentage composition of any given compound is defined as the ratio of the amount of each element present in the given compound to the total amount of individual elements present in that particular compound multiplied by 100. The importance of this composition calculation is found in the chemical analysis.
Percentage Composition Formula
The percentage composition of a given element can be expressed by using the formula given below:
% of an element = (mass of element/molecular mass) x 100
The reason that we multiply this ratio by 100 is to get the percentage form of the given composition.
Percent composition is calculated from a molecular formula that is by dividing the mass of a single element in one mole of a compound by the mass of one mole of the whole given compound. This value is presented in the form of a percentage.
How to Calculate Percentage Composition?
Calculate the percent composition of each element in water.
The chemical formula for water is written as H2O and The molar mass of Oxygen is = 16.00 × 1(one molecule of oxygen is present in water) = 16 g/mole and the molar mass of Hydrogen is = 1.01 × 2(2 molecules of hydrogen are present in water) = 2.02 g/mole
Now, with the help of the molar mass of each of the given elements, find the percentage composition of each element present in H2O.
It is defined as the ratio of the grams of the element to the grams of the total element in that particular compound, multiplied by 100.
Thus, calculating the percentage composition of Hydrogen,
% H = 2.02/18.02 × 100
Consequently,
% H= 11.21 %
The percentage composition of Oxygen is calculated, So,
% O = 16/18.02 ×100 = 88.79 %
Mass Percentage Composition
The concept of mass percentage composition is used to represent the concentration of an element in a compound or the concentration of a component in a given mixture. We use this term to indicate the total percent by mass of each element that is present in a given compound.
The mass percentage composition can be calculated by dividing the mass of a component by its the total mass of the mixture. This ratio obtained is then multiplied by 100.
Importance of Mass Percentage
For many technical and scientific reasons, it is important to know what quantity of an element is present in an assumed compound.
This is crucial for pharmacists to get to the empirical formula of some compounds.
This formula also helps in displaying the lowest whole number of moles and the relative quantity of atoms of each element present in a particular compound.
With the help of this empirical formula, pharmacists can also calculate the actual molecular formula which shows the exact number of atoms present in the given compound.
Determining the Mass Percent from a Chemical Formula
Calculate the mass percent of glucose.
The chemical formula for glucose is written as C6H12O6. Now, calculate the mass percent of each of the elements present in glucose.
From the formula mentioned above, it can be observed that Glucose consists of 6 carbon atoms, 12 hydrogen atoms, and at last 6 oxygen atoms. Now multiply each of the atoms present in the glucose molecule by its molar mass.
So, 6 moles of carbon have 12.01g/mol x 6 = 72.06g of Carbon. (1 mole of carbon has a mass of 12.01grams)
Consequently, 12 moles of Hydrogen will have a mass of 12 x 1.008 = 12.096g of Hydrogen. (1 mole of hydrogen has a mass of 1 gram)
Thus, 6 moles of oxygen will have 16.00 x 6 = 96 g of Oxygen. (1 mole of oxygen has a molecular mass of 16 gram)
Hence, 1 mole of glucose (C6H12O6) has a total mass of (adding all the above values); 72.06 +12.096 + 96 = 180.16 g/mol
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