A LEVEL STOICHIOMETRY

The first stage in the manufacture of nitric acid is the oxidation of ammonia by oxygen.

wNH₃ (g) + xO₂ (g) → yNO (g) + zH₂O (g)

Which values for w, x, y and z are needed to balance the equation?

• A

• B

• C

• D

As a simplification, an adult human can be considered to have a daily diet of 1.80 kg of carbohydrate (empirical formula CH₂O). Which mass of carbon dioxide does a person produce each day if all the carbohydrate eaten is digested and oxidised?

• 0.267 kg

• 0.800 kg

• 1.32 kg

• 2.64 kg

The diagram shows the mass spectrum of a sample of naturally-occurring copper. What is the relative atomic mass of this copper?

• 63.3

• 63.5

• 63.6

• 64.0

Which of these samples of gas contains the same number of atoms as 1g of hydrogen

(M_r: H₂, 2)

• 22g of carbon dioxide (M_r : CO₂, 44)

• 8 g of methane (M_r CH₄, 16)

• 20 g of neon (M_r : Ne, 20)

• 8 g of ozone (M_r : 0₃, 48)

Most modern cars are fitted with airbags. These work by decomposing sodium azide to liberate nitrogen gas, which inflates the bag.

2NaN₃ → 3N₂ + 2Na

A typical driver's airbag contains 50 g of sodium azide. Calculate the volume of nitrogen this will produce at room temperature.

• 9.2 dm³

• 13.9 dm³

• 27.7 dm³

• 72.0 dm³

Which substance, in 1 mol dm^-3 aqueous solution, would have the same hydrogen ion concentration as 1 mol dm^-3 of hydrochloric acid?

• ethanoic acid

• nitric acid

• sodium hydroxide

• sulphuric acid

The petrol additive tetraethyl-lead (IV), Pb(C₂H₅)₄, is now banned in many countries. When it is completely burned in air, lead (II) oxide, CO₂ and H₂O are formed. How many moles of oxygen are required to burn one mole of Pb(C₂H₅)₄?

• 9.5

• 11

• 13.5

• 27

Chlorine dioxide is produced on a large scale as it is used for bleaching paper pulp. It is made by the following reaction.

2ClO₃^- (aq) + SO₂ (g) → 2ClO₂(g) + SO₄^2-(aq)

How do the oxidation numbers of chlorine and sulphur change in this reaction?

• A

• B

• C

• D

N₂O₄ is a poisonous gas. It can be disposed of safely by reaction with sodium hydroxide.

N₂O₄(g) + 2NaOH(aq) → NaNO₃(aq) + NaNO₂(aq) + H₂O(l)

What is the minimum volume of 0.5 mol dm^-3 NaOH (aq) needed to dispose of 0.02 mol of N₂O₄?

• 8 cm³

• 12.5 cm³

• 40 cm³

• 80 cm³

When a sports medal with a total surface area of 150 cm² was evenly coated with silver, using electrolysis, its mass increased by 0.216 g. How many atoms of silver were deposited per cm² on the surface of the medal?

• 8.0 X 10¹⁸

• 1.8 X 10¹⁹

• 1.2 X 10²¹

• 4.1 X 10²²