CfE Higher Chemistry - Unit 3 - Enthalpy

Using Bond Enthalpies, calculate the standard enthalpy change of combustion of propane, given by the equation:

C₃H₈(g) + 5O₂(g) --> 3CO₂(g) + 4H₂O(l)

• -1680

• 1680

• 840

• -1200

In the presence of bright light, hydrogen and bromine react. One step in the reaction is shown below.

H₂(g) + Br(g) → HBr(g) + H(g)

The enthalpy change for this step can be represented as:

(Bond making as always an exothermic process)

• (H-H bond enthalpy) + (Br-Br bond enthalpy)

• (H-H bond enthalpy) − (Br-Br bond enthalpy)

• (H-H bond enthalpy) + (H-Br bond enthalpy)

• (H-H bond enthalpy) − (H-Br bond enthalpy).

Use the information in your databook to calculate the enthalpy change for the following reaction:

H_2(g) + Cl_2(g) --> 2HCl_(g)

• 172

• 200

• -185

• 450

1. Chloromethane can be produced by the reaction of methane with chlorine.

CH₄(g) + Cl₂(g) --> CH₃Cl(g) + HCl(g)

Using bond enthalpies from the data booklet, calculate the enthalpy change, in kJmol⁻¹, for this reaction

• 26

• -234

• 15

• -115

7. When ethanol is combusted, the only two products are carbon dioxide and water. 3 moles of 02 are combusted

Use bond enthalpies to calculate the enthalpy change for this reaction.

• -1025

• 1025

• -742

• 685

1. 0.22g of propane was used to heat 200cm³ of water. The temperature of water was raised by 35^oC. Calculate the enthalpy of combustion of propane.

• -5852

• -3218

• 2297

• 3456

The Enthalpy of neutralisation can be defined as;

• When mole mole of substance dissolves completely in water

• When one mole of substance burns completely in oxygen

• When 1 mole of water is formed in a neutralisation reaction

The enthalpy of solution can be defined as

• The energy released when 1 mole of solute is dissolved in water

• When 1 mole of solute is fully combusted in oxygen

• When 1mole of water is produced in a neutralisation reaction

• When the temperature of water is raised by 20 degrees celcius

The enthalpy of combustion can be described as

• When 1 mole of solute dissolves in water

• When 1 mole of substance is fully combusted in oxygen

• 1 one mole of water is produced in a neutralisation reaction

10g of NaOH was dissolved in 200ml of water the temperature was raised by 10 degrees. Calculate the enthalpy of solution of sodium hydroxide

• -23.67

• -33.44

• -41.44

• 8.16