## Chemical calculations - Higher - Eduqas

### 1

The value of the Avogadro constant is 6.02 x 1023. This means that there are 6.02 x 1023…what?

### 2

How many atoms are there in 1 mol of water molecules (H2O)? (The value of the Avogadro constant is 6.02 x 1023)

### 3

What is the equation showing the number of moles present in a substance?

### 4

What is the mass of 4 mol of carbon dioxide molecules? (Mr of carbon dioxide = 44)

### 5

A piece of sodium is added to a beaker of water. The sodium completely reacts, producing hydrogen gas. Which substance is in excess in this reaction?

### 6

A sample of the compound hydrogen sulfide contained 0.05 mol of hydrogen atoms and 0.025 mol of sulfur atoms. What is the empirical formula of hydrogen sulfide?

### 7

What is the mass of 3 mol of N2O5 molecules? Use these Ar values: N = 14 and O = 16

### 8

A sample of a compound contains 0.20 mol of carbon atoms and 0.80 mol of hydrogen atoms. What is its empirical formula?

### 9

In an experiment, 0.12 g of magnesium reacts with oxygen to make 0.28 g of magneisum oxide. How many moles of oxygen molecules took part in the reaction? Use these Ar values: Mg = 24 and O = 16.

### 10

2.4 g of carbon reacts with 0.6 g of hydrogen to make a compound. What is the empirical formula of the compound? The mass of one mole of carbon atoms is 12 g, and the mass of one mole of hydrogen atoms is 1 g.