A student uses a calorimetry experiment to determine the standard enthalpy of combustion of ethanol.

Define the term standard enthalpy change of combustion.

In the experiment, 0.230 g of ethanol was completely burned and the temperature of 100 g of water was found to rise by 15.2 °C. 

Calculate the standard enthalpy change of combustion, Δ_cH, of ethanol. Give your answer in kJ mol^-1 to the nearest whole number.

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

The experimental value for Δ_cH is found to be lower than the data book value. Suggest one reason for this.

The table below shows some enthalpy change of combustion values.

The equation for the formation of propanol is shown below. 

Use the equation and the table to construct a Hess cycle and calculate the enthalpy change of formation of propanol, Δ_fH.

Hydrogen iodide, HI, is a gas that can be produced in a reversible reaction between hydrogen and iodine.

H_2(g) + I_2(g)  ⇌  2HI_(g)     ΔH = -9 kJ mol^-1

Complete the enthalpy profile diagram below for the forward reaction. Include labels for the activation energy (E_a), the enthalpy change of reaction (ΔH) and the formulae of the reactants and products.

The activation energy for the forward reaction is +173 kJ mol^-1. 

Calculate the activation energy for the reverse reaction.

The value for the enthalpy change of this reaction is negative. 

Explain why this means the reaction is exothermic. Use ideas about bond breaking and bond making in your answer.

The table below shows some bond enthalpy data. 

Use the table to calculate a value for the bond enthalpy of the H-I bond.

The enthalpy change for the reaction between sodium carbonate and hydrochloric acid can bet determined using calorimetry.

Na₂CO_3(s)  +  HCl_(aq)  ➔  2NaCl_(aq)  +  CO_2(g)  +  H₂O_(l)

In the experiment, 3.35 g of sodium carbonate is added to 50.0 g of 2.00 mol dm^-3 HCl so that the HCl is in excess. The temperature of the reaction is found to increase by 5.7 °C. 

Calculate the standard enthalpy change of reaction, Δ_rH, giving your answer in kJ mol^-1 and to 3 significant figures.

The specific heat capacity of the reaction mixture, c, is 4.18 J g^-1 K^-1.

What is meant by the term standard enthalpy of formation?

The table below shows some standard enthalpy of formation values.

Use the equation below and the data in the table to set up a Hess cycle and calculate a value for the standard enthalpy of formation, Δ_fH_, for NO.

Ammonia is produced by the Haber process from nitrogen and hydrogen.

N_2(g) + 3H_2(g)  ⇌  2NH_3(g)    ΔH = −92 kJ mol^-1

The table below shows the bond enthalpy values for nitrogen and hydrogen.

Explain the meaning of the term bond enthalpy.

Use the equation and the table above to calculate a value for the bond enthalpy of the N−H bond.

Give your answer to the nearest whole number.

The data book value for the N−H bond is 388 kJ mol^-1. 

Give one reason for the difference between this value and the value you calculated in part b).

The table below shows some standard enthalpy of formation values. 

Use the table and the equation below to set up a Hess cycle to calculate a value for the enthalpy change of formation, Δ_fH, of NH₃.

Ethanoic acid and sodium hydroxide react according to the equation shown below.

CH₃COOH_(aq) + NaOH_(aq) ➔ CH₃COONa_(aq) + H₂O_(l)    ΔH = −56.1 kJ mol^-1

A student reacted 50.0 cm³ of 2.00 mol dm^-3 ethanoic acid with 50.0 cm³ of 2.00 mol dm^-3 sodium hydroxide. 

Calculate the temperature rise to three significant figures.

Assume both solutions started at the same initial temperature and have a density of 1.00 g cm^-3.

The specific heat capacity of the reaction mixture, c, is 4.18 J g^-1 K^-1.

State what is meant by the term mean bond enthalpy for an O−H bond.

Calculate the enthalpy of formation of water using the bond enthalpies in the table below.

The enthalpy change of reaction, Δ_rH, can be calculated using mean bond enthalpies.

Explain the meaning of the term mean bond enthalpy.

The table below shows some mean bond enthalpy data. 

Use the table and the equation below to calculate a value for the bond enthalpy of the O=O bond.

C₂H₅OH_(g) + 3O_2(g) ➔ 2CO_2(g) + 3H₂O_(g)  ΔH = −1,279 kJ mol^-1

The temperature of 75.0 g of water was found to increase by 5.80°C when 1.80 x 10^-3 moles of pure ethanol was burned in air. 

Calculate the enthalpy change of combustion, Δ_cH, when 1.00 mole of ethanol is burned. 

Give your answer in kJ mol^-1 and to the nearest whole number.

Give two reasons why the value calculated in part c) is different from the data book value which is −1,279 kJ mol^-1.

To determine the enthalpy change of reaction when magnesium reacts with copper sulfate solution, a student sets up a calorimetry experiment. They measure the initial temperature of 25.0 cm³ of 0.750 mol dm^-3 copper sulfate solution to be 21.3 °C. The student then adds an excess of magnesium, stirs the mixture and records the final temperature to be 63.2 °C.

Calculate the enthalpy change of reaction, Δ_rH, in kJ mol^-1, giving your answer to 3 significant figures.

The specific heat capacity of the reaction, c, is 4.18 J g^-1 K^-1, the density of the solution is 1.00 g cm^-3.

The enthalpy change of formation, Δ_fH, can be calculated indirectly from enthalpy changes of combustion, Δ_cH.

Use the enthalpy change of combustion data in the table above to calculate the enthalpy change of formation, Δ_fH_, of nonane.

State the standard conditions for temperature and pressure used in standard enthalpy measurements.

The bond enthalpy for carbon monoxide can be determined using mean bond enthalpy data for the reaction below. 

CH_4(g) + H₂O_(g) ➔ CO_(g) + 3H_2(g)     ΔH = +210 kJ mol^-1

Use the data in the table below to calculate a value for the bond enthalpy of CO.

Some oxides of nitrogen and sulfur are environmental pollutants linked to acid rain.

The standard enthalpy change of formation for NO₂ is +3.2 kJ mol^-1.

Explain why this enthalpy change is endothermic, using ideas about bond breaking and bond making in your answer.

Draw a fully labelled enthalpy profile diagram below for the formation of NO₂ from its elements. Include labels for the activation energy (E_a), the enthalpy change of reaction (ΔH) and the formulae of the reactants and products.

The bond enthalpy of the O=O bond is 496 kJ mol^-1. 

Use the equation below to calculate the mean bond enthalpy for the S=O bond.

Assume both SO₂ and SO₃ only contain S=O bonds.

2SO_2(g) + O_2(g) ➔ 2SO_3(g)   ΔH = −192 kJ mol^-1

This question is about calculating enthalpy changes using Hess's Law.

State Hess's Law.

Use the standard enthalpy of formation values in the table below to calculate a value for the standard enthalpy of reaction, Δ_rH_, when iron oxide is reduced by carbon monoxide to produce iron.

The table below shows some standard enthalpy of formation values for three substances.

Use the equation below and the data in the table above to calculate a value for the standard enthalpy of formation, Δ_fH_, of propanol, C₃H₇OH.

This question is about enthalpy data relating to the combustion of some alkanes.

A calorimetry experiment is used to determine the standard enthalpy of combustion, Δ_cH, of hexane. 

Use the experimental data below to calculate a value for Δ_cH of hexane, giving your answer to 3 significant figures.

Mass of hexane = 1.34 g

Mass of water heated = 150 g

Initial temperature of water = 21.6 °C

Final temperature of water = 65.8 °C

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

The table below shows some standard enthalpy of formation values for three substances.

Use the equation below and data in the table above to calculate a value for the standard enthalpy of combustion, Δ_cH_, of cyclohexane.

Give two reasons why the value calculated in part b) may be different to the data book value.

Use the bond enthalpy data in the table below to calculate a value of the bond enthalpy of the C−O bond in propanol.

C₃H₇OH_(g) + $\frac{9}{2}$O_2(g) ➔ 3CO_2(g) + 4H₂O_(g)   ΔH = −1,893 kJ mol^-1