# GCSE: OCR gateway: C3: Reacting masses

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• C2
• Rate of reaction
• Explosions and Surface Area
• Combustable powders cause explosions
• Some powders react with oxygen to make large volumes of CO2 and water vapour
• Owners of factories using combustable powders (flower) ensure powders cannot reach the atmosphere and that a spark being produced near the powders is small
• As the surface area of a reactant is increased so is it's rate of reaction; more collisions per second
• Catalysts and Rates of Reaction
• Changes the rate of reaction and is unchanged at the end of the reaction
• Only a small quantity of catalyst is needed to catalyse a large amount of reactants
• Each catalyst is specific to a paticular reaction
• Reacting masses
• Relative Formula Mass
• Work out the masses inside of the braket
• Multiply the total by the number outside of the brackets
• Work out the remaining number
• 164
• 40 + 124
• Ca(62*2)
• Ca(14+(16*3))2
• Ca(NO3)2 Ca=40 N=14 O=16
• 40 + 124
• Ca(62*2)
• Ca(14+(16*3))2
• Ca(NO3)2 Ca=40 N=14 O=16
• Conservation of Mass
• Mass of reactants equal to products
• Predicting the Yield of a Reaction
• Write balanced symbol equation
• Find atomic masses of the elements
• Find amount needed to make 1g of product
• Multiply up to the amount of reactant needed
• (80g*20g)/124g = 12.9g
• 80g/124g CuCO3 makes 1g of CuO
• 124g of CuCO3 makes 80g of CuO