## How are the amounts of substances in reactions calculated? - OCR 21C

### 1

In a closed system, how does the total mass of the products of a reaction compare with the total mass of the reactants?

### 2

What is the relative formula mass of magnesium oxide, MgO? (Relative atomic masses: Mg = 24.3, O = 16.0)

### 3

What is the relative formula mass of MgCO3? (Relative atomic masses: Mg = 24.3, C = 12.0, O = 16.0)

### 4

What is the value of the Avogadro constant?

### 5

The definition of the mole states that the number of particles in one mole of a substance are the same as in 12 g of what?

### 6

How many moles of atoms are there in 8.0 g of helium atoms? (Relative atomic mass: He = 4.0)

### 7

How many moles of molecules are there in 64.0 g of oxygen molecules, O2? (Relative atomic mass: O = 16.0)

### 8

Rearrange this equation to make mass the subject: number of moles = mass ÷ relative formula mass.

### 9

If 92.0 g of Na reacts with 32.0 g of O2, what is the reacting ratio of Na:O2? (Relative masses: Na = 23.0 and O2 = 32.0)

### 10

Calcium carbonate decomposes when heated: CaCO3 → CaO + CO2. What mass of CaO can form from 100.1 g of CaCO3? (Relative formula masses: CaCO3 = 100.1, CaO = 56.1)