Energetics (DP IB Chemistry: SL)

A student mixed 30.0 cm³ of 0.0250 mol dm^-3 potassium hydroxide solution with 30.0 cm³ of 0.0250 mol dm^-3 nitric acid. The temperature rose by 0.50 ^oC. Assume no heat was lost to the surroundings. 

The mixture had a specific heat capacity of 4.18 J g ^-1 K^-1. 

What is the molar enthalpy change for the reaction?

An experiment was carried out to determine the approximate value for the molar enthalpy change of neutralisation. 

75 cm³ of 3.00 mol dm^–3 hydrochloric acid was placed in a polystyrene beaker of negligible heat capacity. Its temperature was recorded, and then 75 cm³ of
3.00 mol dm⁻³ potassium hydroxide at the same temperature was quickly added, and the solution stirred. 

The temperature rose by 14 °C. The resulting solution may be considered to have a specific heat capacity of 4.18 J g^-1 K^-1. 

Which calculation below is correct?

The table below discusses three types of enthalpy change:

‘+’ means that this type of standard enthalpy change can only have positive values,

‘–’ means that this type of standard enthalpy change can only have negative values,

‘+ / –’ means that either positive or negative values are possible. 

Which row is correct?

Using a spirit burner, ethanol is used to heat a container of water.

In this experiment:

How much heat energy is absorbed by the water? 

An iron block with a mass of 0.11 kg absorbs 504 J of heat energy. What is the temperature rise in K?

Specific heat capacity of iron = 0.448 J g^–1 K^–1

Which statements are correct for an endothermic reaction? 

1. The products are more stable than the reactants
2. The enthalpy change is positive
3. The temperature of the surroundings decreases

Which assumptions are correct when calculating the enthalpy change for a reaction in solution? 

1. The density of the solution is 1 g cm^-3
2. The specific heat capacity of the solution is 4.18 J g^-1 K^-1
3. The correct stoichiometric quantities of reactants for a complete reaction are used 

What is the closest integer value of the temperature change for this reaction, from the graph

Which enthalpy changes correctly describe the following reactions? 

Reaction 1: HNO₃ (aq) + NH₃ (aq) → NH₄NO₃ (aq)

Reaction 2: CuCO₃ (s) → CuO (s) + CO₂ (g)

Reaction 3: S (s) + O₂ (g) → SO₂ (g)

Which systems are correctly described? 

1. Matter and energy can be transferred across the boundary of an open system
2. Only matter can be transferred across the boundary of a closed system
3. Matter and energy cannot be transferred across the boundary of an isolated system

In a calorimetric experiment 2.50 g of a fuel is burnt in oxygen. 30 % of the energy released during the combustion is absorbed by 500 g of water, the temperature of which rises from 25 °C to 68 °C. 

The specific heat capacity of water is 4.2 J g^–1 K^–1. 

What is the total energy released per gram of fuel burnt?

The reaction of hydrochloric acid with sodium hydroxide produced an overall temperature increase of 24.4 K. 

Given the following data, how much thermal energy was evolved during this reaction? 

Initial temperature of 25.0 cm³ hydrochloric acid = 17.6 ^oC

Initial temperature of 25.0 cm³ sodium hydroxide = 18.5 ^oC 

The specific heat capacity of water is 4.18 J g^-1 K^-1.

The temperature rise when 0.1 MJ of heat energy is absorbed by 2.5 kg of solid aluminium is 44.4 ^oC. 

What is the specific heat capacity of aluminium, in J g^-1 K^-1?

An iron cube, with a mass of 0.5 kg, increases in temperature by 12.7 K when heated. 

The specific heat capacity of iron is 0.448 J K^-1 g^-1. 

What is the enthalpy change, in kJ mol^-1, for heating the iron cube?

When completing experiments to measure enthalpy change for exothermic processes, which of the following is not a reason for the experimental data to be lower than the expected value?

Heptathiepane, S₇, can undergo complete combustion to form sulfur dioxide. 

S₇ (s) + 7O₂ (g) → 7SO₂ (g) 

Which enthalpy changes can be used to describe this reaction?

A student obtained the following experimental results for the enthalpy of combustion of cyclohexane (C₆H₁₂). 

The student determined from this experiment that the enthalpy of combustion of cyclohexane is –1216 kJ mol^–1 

The specific heat capacity of water = 4.18 J g^–1 K^–1
The relative molecular mass (M_r) of cyclohexane = 84.18 

Which calculation will correctly determine the final temperature of the water in this experiment?

The diagrams below show a simple calorimeter that is commonly used in the school laboratory and the more accurate chamber calorimeter.

Which of the following statements correctly explain why the chamber calorimeter is more accurate? 

1. There is less heat loss
2. There is more complete combustion
3. There is less fuel lost

Which of the following assumptions are correct when completing the calorimetry experiment and subsequent calculations for the neutralisation of 25.0 cm³ sulfuric acid by 25.0 cm³ barium hydroxide? 

1. That both solutions have the same initial temperature
2. The value of m in q = mcΔT is 50 g
3. Heat is lost to the surroundings

The heat produced by the combustion of magnesium is used to heat some water. 

Which values are needed to calculate the energy transferred during the reaction? 

1. The mass of magnesium
2. The mass of the water
3. The temperature change of the water