M3S5 – Enthalpy Changes Year 1

An example of an endothermic change is the:

For which of the following equations is the value for standard enthalpy change equal to the standard enthalpy of formation of sodium chloride?

What are the standard conditions for measuring standard enthalpy changes?

The total heat capacity of a calorimeter is 2000 J K^-1.

The standard enthalpy of combustion of propane is -2200 kJ mol^-1

Calculate the expected temperature rise on heating the calorimeter by burning 0.0500 mol of fuel from a propane burner assuming that all the energy heats the calorimeter.

Take care with units.

The standard enthalpy of combustion of methane is -890 kJ mol^-1. Calculate the energy given out on burning 3.2 g methane.

Hydrazine burns according to this equation: N₂H_4(g) + O_2(g) -> N_2(g) + 2H₂O_(l)

Calculate the standard enthalpy change for the combustion of hydrazine given that the standard enthalpy of formation of hydrazine is +51 kJmol^-1 and of water is -286 kJ mol^-1

Calculate the value of the standard enthalpy change of formation of methane given that the values for standard enthalpy changes of combustion are -890 kJ mol^-1 for methane, -393 kJ mol^-1 for carbon and -286 kJ mol^-1 for hydrogen gas.

The energy needed to atomise 1 mol of gaseous ethene, C₂H₄ is 2087 kJ mol^-1. Calculate the average bond enthalpy for a C-H bond given that the bond enthalpy for the C=C bond is +347 kJ mol^-1.

Calculate the enthalpy change for the formation of one mole of hydrogen chloride gas from its elements given these average bond enthalpies: H-H bond enthalpy = 435 kJ mol^-1, Cl-Cl bond enthalpy = 243 kJ mol^-1 and H-Cl bond enthalpy = 432 kJ mol^-1

The standard enthalpy change of formation of N₂O_(g) is +82 kJ mol^-1. This shows that