Amount of Substance

• Amount of Substance

  . A mole (mol) is a measure of the number of particles (atoms, ions or molecules) contained in a substance

  . One mole of any substance (element or compound) contains the same number of particles - six hundred thousand billion billion or 6.02 x 10(23). The particles could be atoms, molecules, ions or electrons

  . This value is known as the Avogadro constant

  . The mass of one mole of a substance is its relative atomic mass or relative formula mass in grams
• Key Point

  One mole of any substance (element or compound) will always contain the same number of particles - six hundred thousand billion billion or 6.02 x 10(23). This value is known as the Avogadro constant
• Calculating the Amount of Substance

  . You can calculate the amount of substance (number of moles) in a given mas of a substance using the formula:

  LEARN: amount (mol) = mass of substance (g)/atomic (or formula) mass (g/mol)
• Balanced Equations

  . Balanced equations:

  - show the number of moles of each product and reactant

  - can be used to calculate the mass of the reactants and products

  . The numbers needed to balance an equation can be calculated from the masses of the reactants and products using moles
• Limiting Reactants

  . Sometimes when two chemicals react together, one chemical is completely used up during the reaction

  . When one chemical is used up, it stops the reaction going any further. It is called the limiting reactant

  . The other chemical, which is not used up, is said to be in excess
• Concentration of solutions

  . The concentration of a solution may be given by the mass of solute per given volume of solution

  . For example, if 2.00g of solute was dissolved to form 1.00dm(3) of solution, the concentration of the solution would be 2.00g/dm(3) (grams per dm(3))