QCE Chemistry Unit 3 - Topic 1

The equilibrium constants of four different reactions are given. In which reaction does the equilibrium lie furthest to the left?

• A

• B

• C

• D

Phosgene gas (COCl₂) is formed by the reaction above.

Which of the following statements is true for the system at equilibrium?

• Removing Cl_{2 (g)} will increase the yield of phosgene and keep the K_c value constant.

• Adding a catalyst will increase the yield of phosgene and keep the K_c value constant.

• Increasing the pressure will increase the yield of phosgene and keep the K_c value constant.

• Decreasing the temperature will decrease the yield of phosgene and keep the K_c value constant.

Determine the pH of a 0.15 M solution of hydrochloric acid (HCl).

• 0.15

• 0.71

• 0.82

• 1.41

Identify the equivalence point on the titration curve.

• I

• II

• III

• IV

Ammonia gas reacts with oxygen gas in the above equilibrium reaction.

The equilibrium expression for the reaction is

• 
• 
• 
• 

Solution A has a pH of 3 and solution B has a pH of 6. This indicates that solution A is

• less acidic and has 0.5 times the concentration of hydrogen ions in solution B.

• more acidic and has 2 times the concentration of hydrogen ions in solution B.

• less acidic and has 0.001 times the concentration of hydrogen ions in solution B.

• more acidic and has 1000 times the concentration of hydrogen ions in solution B.

Identify the numbers on the graph below that represent the activation energy (E_a) for the forward and reverse reactions.

• Forward = 1 Reverse = 3

• Forward = 2 Reverse = 1

• Forward = 2 Reverse = 3

• Forward = 3 Reverse = 4

Which of the following 1.00 mol dm^–3 acid solutions will dissociate to produce the largest concentration of hydrogen ions?

• nitric acid (HNO₃)

• sulfuric acid (H₂SO₄)

• ethanoic acid (CH₃COOH)

• carbonic acid (H₂CO₃)

Predict the effect that increasing the temperature will have on the above reaction.

• The equilibrium position will not change.

• The equilibrium position will move towards the reactants (left).

• The equilibrium position will move towards the products (right).

• It is impossible to predict the effect on the equilibrium position.

The graph shows the pH changes during the titration of 10.0 cm³ of a weak base with 0.10 mol dm^-3 HCl.

The initial concentration of OH^- ions in the weak base is

• 10.5 mol dm^-3

• 3.5 mol dm^-3

• 10^-3.5 mol dm^-3

• 10^-10.5 mol dm^-3