1.7 Quantitative Chemistry Flashcards
Symbol for Relative atomic mass
Ar
What is the Relative formula Mass
The sum of the Relative atomic mass of all atoms present in the formula of the substance. (Sometimes known as relative molecular mass)
Equation for percentage of an element in a compound
% of element in a compound = mass of element in compound
————————————- x 100
relative formula mass
The mass of one mole in substance in grams
Numerically equal to the relative formula mass
Number of Moles in a substance =
Mr
When calculation the moles the mass must always be in grams
use the following to convert them
1 tonne = 1000kg
1 kg = 1000g
Calculating the reacting masses of reactants or products using a balanced equation
Convert the mass given into moles
Use the ratio in the balanced equation to work out moles
Convert the moles of material into mass
What is the meaning of theoretical yield
The maximum possible mass of a product that a chemical reaction can make
What is the meaning of actual yield
The mass of a product that a chemical reaction makes in real life
Main reasons why the percentage yield is not 100% is
Loss during separation
Side reactions may occur
Some reactions do not go to completion
Equation for percentage yield
Actual yield
———————- x 100
Theoretical yield
What is the limitans reactant
The reactant that is all used up
The reactant left over is described as
being in excess
Limiting reactant
Find the number of moles of each reactant
Find the limiting reactant
Use the limiting reactant to work out the number of moles of product
