Chemistry calculations,moles and yield

If the mass seems to change, there's usually a gas involved. 

If the mass increases:

• One of the reactants is a gas found in air and all the products are solids, liquids or aqueous. 

If the mass decreases:

• One of the products is a gas and all the reactants are solids, liquids or aqueous.

• divide the mass of each substance by it's relative formula mass to find the number of moles.
• divide the number of moles of each substance by the smallest number of moles in the reaction.
• If any of the numbers aren't whole numbers, multiply all the numbers by the same amount so that they all become whole numbers.
• Write the balanced symbol equation by putting these numbers in front of the chemical formulas.