# The Mole and Equations

• Created by: India.02
• Created on: 27-04-19 19:18
• The Mole and Equations
• Reactants Used Up
• When magnesium carbonate reacts with hydrochloric acid, bubbles of gas are produced
• The reaction stops when one of the reactants has been used up - any other reactants are in excess
• Usually in excess to make sure that the other reactant gets used up
• Reactant that is used up is called the limiting reactant - because it limits the amount of product formed
• The amount of product formed is directly proportional to the amount of limiting reactant - if you half the limiting reactant then you half the products
• If you add more reactant then there are more reactant particles to take part in the reaction - more product particles
• One Mole of Gas
• At the same temperature and pressure, equal numbers of moles of any gas will occupy the same volume
• At 20 degrees celsius and 1 atm, one mole of any gas occupies 24dm*3
• Volume of gas
• Amount of Product
• 1. Write out balanced equation - work out relative formula masses of reactant and product that you want - find how many moles there are of the substance you know the mass of
• 2. Use balanced equation to work out how many moles there will be of the other substance - use number of moles to calculate mass
• Balanced Equations
• Big numbers in front of the chemical formulas tell you how many moles there are of each substance
• Little numbers show how many atoms of each element are in the substance
• If you know the masses of the reactants and the products, you can work out the balanced equation
• 1. Divide mass of each substance by it's relative formula mass to find number of moles - divide number of moles of each substance by the smallest number of moles in the reaction
• 2. if any of the numbers aren't whole numbers, multiply them all by the same number so that they all become whole numbers - write the balanced symbol equation