W1 Aug C-S4D Pure Chem - Mole concept + Chem calc

25 cm³ of 1.20 mol/dm³ hydrochloric acid was required to fully neutralise 20 cm³ of sodium hydroxide solution with an unknown concentration.

What is the concentration of the sodium hydroxide solution?

• 0.96 mol/dm³

• 1.0 mol/dm³

• 1.5 mol/dm³

• 1.6 mol/dm³

Copper reacts with concentrated nitric acid as shown in the equation below:

Cu (s) + 4HNO₃ (aq) → Cu(NO₃)₂ (aq) + 2NO₂ (g) + 2H₂O (l)

A 75 g piece of gold, sample G was placed in excess concentrated acid. The volume of nitrogen dioxide evolved was measured to be 7200 cm³ at r.t.p. 

What is the percentage purity of sample G?

• 42.0%

• 69.3%

• 74.2%

• 87.2%

20 cm³ of methane was reacted with 50 cm³ of oxygen.

CH₄ (g) + 2O₂ → CO₂ (g) + 2H₂O (l)

What is the final volume of gas present at room temperature and pressure?

• 20 cm³

• 30 cm³

• 60 cm³

• 70 cm³

A sample of a certain CFC contains 14.0% of carbon, 41.5% of chlorine and 44.5% of fluorine by mass.

If the CFC has a molecular mass of 171, what is its molecular formula? You may use the table provided to help you.

• CClF₂

• C₂Cl₂F₄

• C₃Cl₃F₆

• C₄Cl₄F₈

25 cm³ of 1.5 mol/dm³ hydrochloric acid was added to an excess of solid sodium carbonate as seen in the equation below: 

2HCl (aq) + Na₂CO₃ (s) -> 2NaCl (aq) + H₂O (l) + CO₂ (g)

Using stoichiometry, what was the mass of sodium carbonate that reacted with the hydrochloric acid?

• 1.98 g

• 1.99 g

• 2.00 g

• 2.01 g

Water is formed from the reaction of hydrogen with oxygen. This reaction is described by the equation below:

2H₂ (g) + O₂ (g) → 2H₂O (l)

What is the mass of oxygen gas required to fully react with 32.0 cm³ of hydrogen gas?

(a)