Monitoring Chemical Reactions (OCR GCSE Chemistry A (Gateway))

A solution of CuSO₄ has a concentration of 35 g/dm³.

What mass of CuSO₄ would there be in 250 cm³ of the solution?

In a titration 25.00 cm³ of 0.20 mol/dm³ sodium hydroxide reacted with 26.50 cm³ of hydrochloric acid.

HCl + NaOH  → NaCl + H₂O

What is the concentration of the acid?

A student titrated 25.00 cm³ of 0.40 mol/dm³ potassium hydroxide solution against sulfuric acid and found that 23.55 cm³ of the acid was required to reach the end point.

H₂SO₄ + 2KOH  →  K₂SO₄ + 2H₂O

What is the concentration of the sulfuric acid?

What is the volume occupied by 5.6 g of nitrogen gas at RTP?

Relative atomic masses (A_r): N = 14

The reaction between nitrogen and hydrogen produces ammonia.

N₂ (g) + 3H₂ (g)   2NH₃ (g)

What volume of ammonia is produced from 565 cm³ of hydrogen?

Air bags contain sodium azide (NaN₃) which decomposes on heating to form sodium and nitrogen.

2NaN₃       →       2Na       +       3N₂

What volume of nitrogen would be produced from 13 g of sodium azide?

Relative atomic mass (Ar): N = 14

Relative formula mass (M_r): NaN₃ = 65

A gas cylinder has a volume of 264 dm³.   

What mass of hydrogen does it contain?

Relative atomic masses (A_r): H = 1

A student made magnesium oxide by reacting 2.4 g of magnesium with steam:

Mg (s) + H₂O (g)  → MgO (s) + H₂ (g)

She calculated the theoretical yield should be 4.0 g of magnesium oxide, but she only obtained 3.2 g.

What was the percentage yield for the experiment?

Hydrogen gas, H₂, reacts with oxygen gas, O₂, to make water, H₂O.

2H₂ + O₂ → 2H₂O

What is the atom economy for this reaction?

M_r : H₂ = 2, O₂ = 32, H₂O = 18.

A student is making a fertiliser called potassium nitrate, KNO₃.

Look at the equation for the reaction she uses.

KOH + HNO₃ ➞ KNO₃ + H₂O

The relative formula masses, M_r, of each compound are shown in the table.

What is the atom economy for the reaction to make potassium nitrate?

Assume that water is a waste product.

Higher Only

In the Haber process, nitrogen reacts with hydrogen to make ammonia.

N₂ (g) + 3H₂ (g) ⇌ 2NH₃ (g)

What is the maximum volume of ammonia, NH₃, that can be made from 150 cm³ of hydrogen, H₂?

Higher Only

Which is the correct expression for calculating the concentration of a solution in g / dm³?

Higher Only

Zinc nitrate thermally decomposes to give two gases.

2Zn(NO₃)₂ (s) → 2ZnO (s) + 4NO₂ (g) + O₂ (g)

A student heats 1.89 g of zinc nitrate until there is no further reaction.

What is the total volume of gas measured at room temperature and pressure, made in this reaction?

• Assume that one mole of gas occupies a volume of 24 dm³ at room temperature and pressure.

• The molar mass of zinc nitrate is 189 g/mol.

Higher Only

How much 0.2 mol / dm³ hydrochloric acid solution could you make from 100 cm³ of 1.0 mol / dm³ hydrochloric acid?

Higher Only

Which procedure is the most suitable for preparing a 0.10 mol / dm³ solution of sodium carbonate?

• The relative formula mass, M_r, of sodium carbonate is 106.

Which of these is/are a factor(s) in choosing a reaction pathway?

A student carrying out a titration finds that a 25.0 cm³ solution of 0.500 mol/dm³ hydrochloric acid neutralises 35.0 cm³ of sodium hydroxide. 

The balanced symbol equation for the reaction is:

NaOH + HCl  →    NaCl  + H₂O

What is the concentration of the sodium hydroxide?

A student made zinc chloride by reacting 15.0 g of zinc carbonate with hydrochloric acid.

ZnCO₃ + 2HCl →  ZnCl₂ + CO₂ + H₂O

The percentage yield of zinc chloride was 82.4%.

Calculate the mass of zinc chloride the student actually produced.

Relative atomic masses (A_r): C = 12    Zn = 65   O = 16    Cl = 35.5     H = 1