1. 2H2SO4 + 2CsOH —> Cs2SO4 + 2H2O
Work out the mass of the missing reactant/product
KOH + HBr —> KBr + H2O
13 g + ___ g —> 20 g + 10 g
2H2SO4 + 2CsOH —> Cs2SO4 + 2H2O
___ g + 24 g —> 32 g + 19 g
C5H10 + 5O2 —> 5CO + 5H2O
50 g + 16 g —> ___ g + 40 g
A group of students are heating magnesium
In a crucible. At the start of the experiment
The crucible and magnesium weigh 10g. After heating for a few minutes
The students let their crucible cool. The mass is now 11g.
Explain why:
Chemical Quantities
Balance the following equations:
H2 + O2  H2O
H2 + N2  NH3
Cr + O2  Cr2O3
NaClO3  NaCl O2
When magnesium is heated in air it gains mass. If 2.4 g of magnesium makes 4 g of magnesium oxide, how much oxygen was added from the air?
A reaction is shown to lose mass during an experiment. Explain why.
Relative Atomic Mass (RAM, Ar)
An atom’s mass number is the sum of its _________ and ________. Carbon has 6 neutrons, and 6 protons so we say it has a mass of ______.
Some elements have isotopes. These are the same atom, but with different numbers of __________.
The Carbon-12 Standard
The relative atomic mass of an element is the average mass of an atom of that element compared to the mass of an atom of ______________.
Relative Formula Mass (RFM, Mr)
The RFM of a compound is the sum of all the RAMs of the _____________ in that compound.  

2. Chemical Quantities Mass Changes with Gases in Reactions
Some reactions involve a mass change, seemingly from nowhere. Either an _________ in mass or a ________ can be due to a gas.
If the mass ________ in a reaction then a gas has been given off as a product.
If the mass has __________, then a gas has been used as a reactant.
Mass cannot be _________ or destroyed from nowhere, and so a seemingly __________ mass change can be easily explained.
Increase, created, decrease , increased, drops, random
Find the atomic mass (Mr) of:
Carbon:
Oxygen:
Calculate the formula mass (Mf) of:
CO2:
Na2SO4.:
Pb(NO3)2.:
How much is a mole of:
Carbon atoms
Oxygen atoms:
Put the following solutions into order
With the most dilute first:
20g/100cm3
20g/1000cm3
8g/50cm3
ZnCO3  ZnO + CO2
How many grams of ZnO would be
produced
From 6.25g ZnCO3?
Chemical Quantities
The equation for the reaction of calcium carbonate with hydrochloric acid is:
CaCO3 + 2HCl  CaCl2 + CO2 + H2O
(a)How many moles of hydrochloric acid react with one mole of calcium carbonate?
(b)How many moles of calcium chloride are produced from one mole of calcium carbonate?
(c)What is the mass of calcium chloride that can be made from one mole of calcium carbonate?
(d)What is the mass of one mole of calcium carbonate?

3. 2H2SO4 + 2CsOH —> Cs2SO4 + 2H2O
Work out the mass of the missing reactant/product
KOH + HBr —> KBr + H2O
13 g + 17 g —> 20 g + 10 g
2H2SO4 + 2CsOH —> Cs2SO4 + 2H2O
17 g + 24 g —> 32 g + 19 g
C5H10 + 5O2 —> 5CO + 5H2O
50 g + 16 g —> 26 g + 40 g
A group of students are heating magnesium
In a crucible. At the start of the experiment
The crucible and magnesium weigh 10g. After heating for a few minutes
The students let their crucible cool. The mass is now 11g.
Explain why: Magnesium has reacted with oxygen in the air to produce
Magnesium oxide.
Balance the following equations:
2H2 + O2  2 H2O
3H2 + N2  2 NH3
4Cr + 3O2  2Cr2O3
2NaClO3  2 NaCl + 3 O2
Chemical Quantities-
Answers
When magnesium is heated in air it gains mass. If 2.4 g of magnesium makes 4 g of magnesium oxide, how much oxygen was added from the air?
1.6g
A reaction is shown to lose mass during an experiment. Explain why.
A gas is given off
Relative Atomic Mass (RAM, Ar)
An atom’s mass number is the sum of its protons and neutrons. Carbon has 6 neutrons, and 6 protons so we say it has a mass of 12.
Some elements have isotopes. These are the same atom, but with different numbers of neutrons.
The Carbon-12 Standard
The relative atomic mass of an element is the average mass of an atom of that element compared to the mass of an atom of carbon 12.
Relative Formula Mass (RFM, Mr)
The RFM of a compound is the sum of all the RAMs of the atoms in that compound.  

4. Chemical Quantities – Answers
Mass Changes with Gases in Reactions
Some reactions involve a mass change, seemingly from nowhere. Either an increase in mass or a decrease can be due to a gas.
If the mass decreases in a reaction then a gas has been given off as a product.
If the mass has increased, then a gas has been used as a reactant.
Mass cannot be created or destroyed from nowhere, and so a seemingly random mass change can be easily explained.
Increase, created, decrease , increased, drops, random
Find the atomic mass (Mr) of:
Carbon: 12
Oxygen: 16
Calculate the formula mass (Mf) of:
CO2: 44
Na2SO4.: 142
Pb(NO3)2.: 331
How much is a mole of:
Carbon atoms: 12g
Oxygen atoms: 16g
CO2: 44g
Na2SO4.: 142g
Pb(NO3)2.:331g
Put the following solutions into order
With the most dilute first:
20g/100cm3 3
20g/1000cm3 1
8g/50cm3 2
ZnCO3  ZnO + CO2
How many grams of ZnO would be
produced
From 6.25g ZnCO3?
RFM ZnCO3 = 125
6.25g = 0.05 mol
1:1
1 mol ZnO = 81g mol = 4.05g
Chemical Quantities –
Answers
The equation for the reaction of calcium carbonate with hydrochloric acid is:
CaCO3 + 2HCl  CaCl2 + CO2 + H2O
(a)How many moles of hydrochloric acid react with one mole of calcium carbonate? 2
(b)How many moles of calcium chloride are produced from one mole of calcium carbonate? 1
(c)What is the mass of calcium chloride that can be made from one mole of calcium carbonate?
1 mole calcium chloride = 40 + (35.5 x 2) = 110g
(d)What is the mass of one mole of calcium carbonate?
100g