11 Chemistry Data Test Practice

Which number on the titration curve represents the equivalence point?

• 1

• 2

• 3

• 4

Answer explanation

The equivalence point is the midpoint of the vertical line (where the pH abruptly changes)

Which number on the titration curve represents the half-equivalence point?

• 1

• 2

• 3

• 4

Answer explanation

The half-equivalence point is the pH at half the volume of the equivalence point

What type of titration is represented?

How do you know?

• Strong acid, weak base

  Equivalence point pH > 7

• Strong acid, weak base

  Equivalence point pH < 7

• Weak acid, strong base

  Equivalence point pH < 7

• Weak acid, strong base

  Equivalence point pH > 7

Answer explanation

The strong acid completely ionises into H+ ions, while the weak base will only partially ionise into OH- ions. Therefore, there will be more H+ ions than OH- ions, so at the equivalence point (mol of acid = mol of base) there will be excess H+ ions, contributing to the lower pH.

A 25.0 mL aliquot of NH₃ is titrated with 0.150 M HCl, and the titration curve is given. Calculate the concentration of the NH₃.

Use the Acid-base indicator table on page 14 of the Formula and Data book to infer which indicator would be suitable for this titration.

Answer explanation

Methyl red has a pH range of 4.4 - 6.2, which means it will change colour over the equivalence point pH of 5.6

A mixture of the gases carbon monoxide, chlorine and phosgene (COCl2) was placed in a closed vessel of fixed volume and the equilibrium system was established as shown.

What change occurred at 10 minutes?

• CO(g) was removed

• CO(g) was added

• Volume was decreased

• Volume was increased

Answer explanation

The rapid decrease in CO concentration at 10 minutes (as represented by the vertical line) shows that CO was removed from the system.

A mixture of the gases carbon monoxide, chlorine and phosgene (COCl₂) was placed in a closed vessel of fixed volume and the equilibrium system was established as shown.

What change occurred at 4 minutes?

• Temperature was increased

• Volume was increased

• Volume was decreased

• Temperature was decreased

Answer explanation

As all of the gas concentrations changed gradually the change had to be temperature. [CO] and [Cl2] increased; and [COCl2] decreased, therefore the reverse reaction was favoured. As the forward reaction is exothermic (H = -108 kJ), the reverse reaction must be endothermic. The endothermic reaction is favoured if the temperature increases.

A mixture of the gases carbon monoxide, chlorine and phosgene (COCl₂) was placed in a closed vessel of fixed volume and the equilibrium system was established as shown.

What change occurred at 14 minutes?

• Volume was increased
• Volume was decreased

• Temperature was increased

• Temperature was decreased

Answer explanation

The only change that will rapidly decrease all of the gas concentrations at the same time is if the volume is changed. As the concentrations all decreased, there must be more space for the gas molecules to move around, so the volume was increased.

A mixture of the gases carbon monoxide, chlorine and phosgene (COCl₂) was placed in a closed vessel of fixed volume and the equilibrium system was established as shown.

Calculate K_c at 13 minutes.

Give your answer to 2 d.p.

In a galvanic cell, the electrode with the more positive electrode potential value will be the strongest​ (a)   agent and will undergo​ (b)   and is called the (c)   .

• oxidation
• anode
• reducing
• oxidising
• cathode
• reduction