Year 12 Chemistry Chapter 17

The table shown to the left contains the percentage composition by mass of the nutritional value of some common foods.

Which one of the following servings has the highest energy content?

• 100 g of fish

• 80 g of bread

• 40 g of cheese

• 258 g (250 mL) of milk

In the human body, not all energy available from the metabolism of food is dissipated as heat energy. A student

carried out further research on this and found that some of the energy is used in the production of adenine

triphosphate, ATP^3–, from adenine diphosphate, ADP^2–, and inorganic phosphate, PO4^3–, according to the following

equation.

ADP^2– + PO4^3– + 2H⁺ → ATP^3– + H2O

The student also learnt that the overall equation for aerobic respiration can be represented as shown below.

C₆H₁₂O₆ + 6O₂ + 32ADP^2– + 32PO4^3– + 64H⁺ → 6CO₂ + 32ATP^3– + 38H₂O

It is reasonable to deduce that in aerobic respiration

• the formation of ATP^3– is a hydrolysis reaction.

• for 3.3 g of CO₂ to be produced, 0.40 mol of ADP^2– is needed [M(CO₂) = 44 g mol^–1].

• the production of ATP^3– from ADP^2– and PO₄^3– is an exothermic reaction.

• 9.5 g of C₆H₁₂O₆ will produce 2.0 mol of ATP^3– [M(C₆H₁₂O₆) = 180 g mol^–1].

The thermochemical equation for the complete combustion of glucose is

• C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O ΔH = −2860 kJ mol⁻¹

• C₆H₁₂O₆ + 3O₂ → 6CO + 6H₂O ΔH = −2011 kJ mol⁻¹

• C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ ΔH = −69 kJ mol⁻¹

• C₆H₁₂O₆ → 2C₃H₆O₃ ΔH = −120 kJ mol⁻¹

The calibration factor of a bomb calorimeter was determined by connecting the calorimeter to a power supply. The

calibration was done using 100 mL of water, 6.5 V and a current of 3.6 A for 4.0 minutes. The temperature of the

water increased by 0.48 °C during the calibration.

4.20 g of sucrose underwent complete combustion in the bomb calorimeter. The temperature of the 100 mL of water

increased from 19.6 °C to 25.8 °C.

M(C₁₂H₂₂O₁₁) = 342 g mol⁻¹

The experimental heat of combustion of pure sucrose, in joules per gram, is

• 5.9 × 10⁶

• 7.3 × 10⁴

• 1.7 × 10⁴

• 1.2 × 10⁴

A solution calorimeter containing 350 mL of water was set up. The calorimeter was calibrated electrically and the graph of the results is shown to the left.

The calorimeter was calibrated using a current of 2.7 A, starting at 60 s. The current was applied for 180 s and the applied voltage was 5.4 V.

What is the calibration factor for this calorimeter?

• 125 J °C⁻¹

• 820 J °C⁻¹

• 847 J °C⁻¹

• 875 J °C⁻¹

A solution calorimeter containing 350 mL of water was set up. The calorimeter was calibrated electrically and the graph of the results is shown to the left.

The calorimeter was calibrated using a current of 2.7 A, starting at 60 s. The current was applied for 180 s and the applied voltage was 5.4 V.

This type of calorimeter

• has no heat loss.

• can be used for bomb calorimetry.

• requires electrical calibration in order to determine the calibration factor.

• measures energy changes that can be measured in a bomb calorimeter.

A temperature–time graph from a solution calorimetry experiment is show to the left.

Which one of the following statements related to the graph is incorrect?

• The calorimeter is poorly insulated and lost heat to the surroundings.

• The graph depicts a reaction which has a negative enthalpy change.

• After 4.0 minutes the graph will plateau at a constant value.

• Before mixing, the temperature of the reactant solutions was 18.0°C.

The energy content of peanuts in a particular sample was investigated using two different methods.

• Method 1: A peanut was weighed and set alight. The burning peanut was then held close to a flask containing 25.0 g of water. The temperature of the water increased by 14.2°C by burning 0.113 g of the peanut.

• Method 2: 0.238 g of crushed peanuts were burnt in a bomb calorimeter to produce an increase in temperature of 6.35°C. The energy content of the peanuts was calculated to be 23.1 kJ g^–1.

How many joules of energy were used to heat the water in method 1?

• 8.49

• 1.67 × 10²

• 1.06 × 10³

• 1.48 × 10³

The energy content of peanuts in a particular sample was investigated using two different methods.

• Method 1: A peanut was weighed and set alight. The burning peanut was then held close to a flask containing 25.0 g of water. The temperature of the water increased by 14.2°C by burning 0.113 g of the peanut.

• Method 2: 0.238 g of crushed peanuts were burnt in a bomb calorimeter to produce an increase in temperature of 6.35°C. The energy content of the peanuts was calculated to be 23.1 kJ g^–1.

What is the calibration factor (in J °C–1) of the bomb calorimeter used in method 2?

• 86.6

• 616

• 866

• 925

The nutrition information panel on a packet of muesli includes the information shown to the left.

Using this information, the percentage energy content due to protein in an average serving size of this muesli is

• 31.2%

• 29.3%

• 14.0%

• 13.2%