C3 Quantitative Chemistry
Relative Formula Mass
All the atomic masses of a compound added together
E.g. MgCl2 = 95
Calculating the percentage of Mass of an element in a
compound
MOLEz
The name given to the amount of a substance
1 mole is equal to 6.02 x 1023 atoms
One mole can be atoms, molecules, ions or electrons
Once mole of atoms/molecules will have the same mass in grams as its relative formula mass
SO, 1 MOLE OF CARBON IS EQUAL TO 12 GRAMS
Finding the number of moles in a Given Mass
Practice Questions
1. How many moles are there in 66g of Carbon Dioxide?
2. What mass of carbon is there in 4 moles of carbon dioxide?
3. How many molecules are contained in 0.65 mole of sulphur dioxide, SO2?
4. How many moles of hydrogen contain 5.5 x 1024 molecules of H2?
5. How many molecules are in 150 g of water, H2O?
Conservation of Mass
In a chemical reaction no atoms are created or destroyed
Same number of atoms and types are on both sides of the equation
You can show the conservation of mass by adding up all of the products and reactants on either
side
If the mass changes?
Mass increase- probably because one of the reactants is a gas found in the air
1. Before the reaction the gas is floating around in the air in an uncontained reaction vessel so
its mass isn’t accounted for
Relative Formula Mass
All the atomic masses of a compound added together
E.g. MgCl2 = 95
Calculating the percentage of Mass of an element in a
compound
MOLEz
The name given to the amount of a substance
1 mole is equal to 6.02 x 1023 atoms
One mole can be atoms, molecules, ions or electrons
Once mole of atoms/molecules will have the same mass in grams as its relative formula mass
SO, 1 MOLE OF CARBON IS EQUAL TO 12 GRAMS
Finding the number of moles in a Given Mass
Practice Questions
1. How many moles are there in 66g of Carbon Dioxide?
2. What mass of carbon is there in 4 moles of carbon dioxide?
3. How many molecules are contained in 0.65 mole of sulphur dioxide, SO2?
4. How many moles of hydrogen contain 5.5 x 1024 molecules of H2?
5. How many molecules are in 150 g of water, H2O?
Conservation of Mass
In a chemical reaction no atoms are created or destroyed
Same number of atoms and types are on both sides of the equation
You can show the conservation of mass by adding up all of the products and reactants on either
side
If the mass changes?
Mass increase- probably because one of the reactants is a gas found in the air
1. Before the reaction the gas is floating around in the air in an uncontained reaction vessel so
its mass isn’t accounted for
