Year 12 Chemistry Chapter 3

The kinetic energy of a sample of gas in a container of fixed volume is represented by the distribution curve shown in Graph 1 to the left.

One change was made to the sample and the resulting distribution curve of kinetic energy is shown in Graph 2.

Which one of the following statements explains the change from Graph 1 to Graph 2?

• The average kinetic energy of the gas molecules decreased.

• More gas, at the same temperature, was added to the container.

• More collisions occurred between gas particles.

• The temperature of the gas was increased.

The diagram to the left represents the Maxwell-Boltzmann distribution of an uncatalysed reaction.

The effect of adding a catalyst could be:

1. the curve flattens to reflect the lower activation energy barrier

2. the curve shifts to the right

3. the Ea shifts to the left.

• 1 only

• 1 and 2

• 2 and 3

• 3 only

Use the following information to answer this question.

The heat of combustion of ethanoic acid, C₂H₄O₂, is −876 kJ mol⁻¹ and the heat of combustion of methyl methanoate, C₂H₄O₂, is −973 kJ mol⁻¹. The auto-ignition temperature (the temperature at which a substance will combust in air without a source of ignition) of ethanoic acid is 485 °C and the auto-ignition temperature of methyl methanoate is 449 °C.

Which one of the following pairs is correct?

• 
• 
• 
• 

Use the following information to answer this question.

The heat of combustion of ethanoic acid, C₂H₄O₂, is −876 kJ mol⁻¹ and the heat of combustion of methyl methanoate, C₂H₄O₂, is −973 kJ mol⁻¹. The auto-ignition temperature (the temperature at which a substance will combust in air without a source of ignition) of ethanoic acid is 485 °C and the auto-ignition temperature of methyl methanoate is 449 °C.

If 0.1 mol of ethanoic acid and 0.1 mol of methyl methanoate were completely combusted in two separate closed vessels under identical conditions, the Maxwell-Boltzmann distribution of the product gases from the combustion of

ethanoic acid would be

• broader than the Maxwell-Boltzmann distribution of the methyl methanoate product gases and the chemical

  energy of the product gases would be identical.

• narrower than the Maxwell-Boltzmann distribution of the methyl methanoate product gases and the chemical

  energy of the product gases would be identical.

• broader than the Maxwell-Boltzmann distribution of the methyl methanoate product gases and the chemical

  energy of the ethanoic acid product gases would be higher.

• narrower than the Maxwell-Boltzmann distribution of the methyl methanoate product gases and the chemical

  energy of the ethanoic acid product gases would be higher.

The volume, in L, of CO₂ gas produced from the complete combustion of 1.16 g of butane at 850 °C and 500 kPa will be

• 0.0037

• 0.149

• 0.373

• 1.49

What volume of ethane at standard laboratory conditions (SLC) is required to produce the same amount of energy as 150 g of butane?

• 24.8 L

• 119 L

• 1560 L

• 7460 L

Magnesium carbonate reacts with hydrochloric acid according to the equation below.

MgCO₃(s) + 2HCl(aq) → MgCl₂(aq) + H₂O(l) + CO₂(g)

0.35 g of magnesium carbonate was added to a reaction vessel containing 50.0 mL of 0.2 M hydrochloric acid solution and the carbon dioxide gas produced was collected. The

temperature was 25°C and the atmospheric pressure as 1.0 atm.

Using these conditions, the calculated maximum volume of carbon dioxide is closest to

• 10 mL

• 70 mL

• 100 mL

• 170 mL

Magnesium carbonate reacts with hydrochloric acid according to the equation below.

MgCO₃(s) + 2HCl(aq) → MgCl₂(aq) + H₂O(l) + CO₂(g)

When a student conducted and repeated this reaction, the volume of carbon dioxide collected in each experiment was significantly less than the theoretical maximum.

Which of the following is least likely to contribute to the lower than expected volume?

• Some carbon dioxide dissolves in the water in the gas collection apparatus.

• The pressure of the collected carbon dioxide gas was less than atmospheric pressure.

• The gas collection tubing was not sealed completely at the join to the reaction vessel.

• The temperature of the water used in the gas collection apparatus was 20°C.

10 g of carbon dioxide, CO₂, gas is injected into a sealed, evacuated 12 L vessel at 30 °C. After a further 1 g of CO₂ gas is injected into the vessel, what is the temperature change, in degrees Celsius, required to maintain the original pressure?

• -28

• -3.7

• +3.7

• +28