Chemical energy test questions - Higher Chemistry Revision

1

Which of the following is true for endothermic reactions?

The enthalpy of reactants and products are equal

The enthalpy of the reactants is greater than the enthalpy of the products

The enthalpy of the products is greater than the enthalpy of the reactants

2

Which of these equations represents the enthalpy of combustion of butane (C₄H₁₀)?

\[2\,\,C_{4}H_{10}+13\,\,O_{2}2 \rightarrow 8CO_{2}+10\,\,H_{2}O\]

\[C_{4}H_{10}+13/2\,\,O_{2} \rightarrow 4CO_{2}+5H_{2}O\]

\[C_{4}H_{10}+9/2\,\,O_{2} \rightarrow 4CO+5H_{2}O\]

3

In the equation \(\Delta H=cm \Delta T\), which of the terms is a constant?

\[c\]

\[m\]

\[\Delta T\]

4

3.6 g of butanol (C₄H₉OH) was burned, releasing 134 kJ of energy. What would the enthalpy of combustion of butanol be?

134kJ mol^-1

2754.44kJ mol^-1

-2754.44kJ mol^-1

5

2 g of ethanol (formula mass 46 g) was burned, heating 10 litres of water from 20.2^oC to 21.6^oC. Calculate the enthalpy of combustion of ethanol.

-1345.96 kJmol^-1

-58.52 kJmol^-1

-415.23 kJmol^-1

6

Which of the following is a definition of Hess’s law?

The enthalpy change for a chemical reaction is independent of the route taken

The enthalpy change when one mole of a substance is completely burned in excess oxygen

The enthalpy change per mole of water formed when an acid is neutralised by an alkali

7

Given that the energy change when a carbon to carbon single bond is broken is +346 kJ, what is the enthalpy change when a carbon to carbon single bond is formed from two separate atoms?

346 kJ

-346 kJ

123 kJ

8

In an experiment to calculate the enthalpy of combustion, which of the following does not need to be recorded?

The mass of water

The final temperature of the water

The boiling point of the fuel

9

Why are some bond enthalpies quoted as a 'mean bond enthalpy'?

They are the average of the enthalpies of all the bonds in the molecule

Bonds may have different enthalpies in different molecules

The bond enthalpies cannot be accurately measured

10

The enthalpy changes for the formation of one mole of aluminium oxide and one mole of iron(III) oxide are shown below.

\[2Al(s)+1\frac{1}{2}O_2(g) \rightarrow Al_{2}O_{3}(s)\,\,\,\,\,\,\,\,\,\, \Delta H_{1} \]

\[2Fe(s)+1\frac{1}{2}O_{2}(g)\rightarrow Fe_{2}O_{3}(s)\,\,\,\,\,\,\,\,\,\, \Delta H_{2}\]

Based on these equations, what is the enthalpy change for the following reaction?

\[2Al(s)+Fe_{2}O_{3}(s) \rightarrow Al_{2}O_{3}(s)+2Fe(s)\,\,\,\,\,\,\,\, \Delta H_{T}\]

\[\Delta H_{T}= \Delta H_{1}- \Delta H_{2}\]

\[\Delta H_{T}= \Delta H_{1}+ \Delta H_{2}\]

\[\Delta H_{T}= \Delta H_{2}- \Delta H_{1}\]