The Mole (mol)
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The mole (mol) is the SI unit of measurement for the quantity of a substance. It is defined as the amount of any substance that contains as many elementary entities as there are atoms in 12 grammes of pure carbon-12.
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This number, often referred to as Avogadro’s number, is approximately 6.02214076 × 10^23. This means that one mole of any substance contains approximately 6.022 x 10^23 atomic or molecular entities.
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The concept of the mole can be applied to all types of particles, including atoms, electrons, ions, and molecules.
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The mole is used extensively in stoichiometric calculations. Understanding the mole allows for predictions about the quantities of reactants needed or products formed in a chemical reaction.
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The molar mass of an element is the mass of one mole of the element. It is numerically equal to the atomic mass of the element and is usually expressed in grammes per mole (g/mol).
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The molar volume of a gas is the volume occupied by one mole of the gas. At standard temperature and pressure (STP), 1 mol of any gas occupies 22.4 litres.
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When carrying out calculations involving moles, ensure to consider the balanced chemical equation. The coefficients (numbers in front of) of the balanced equation indicate the ratio of moles involved in the reaction.
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For conversion of mass to moles, use the formula: moles = mass (g) / molar mass (g/mol).
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To determine the number of particles from moles, utilise Avogadro’s number: number of particles = number of moles X Avogadro’s number.
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It’s also essential to understand how moles link to solutions. The concentration of a solution in mol/dm^3 is defined as the amount of solute (in moles) present per dm^3 (litre) of solution.
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Molarity (M) is used to express concentrations in mol/dm^3. It represents the number of moles of a solute in 1 dm^3 of solution. Calculated by dividing the number of moles of solute by the volume of the solution in dm^3.