Chemistry 9701 · AS & A Level · Hydrocarbons

Hydrocarbons — practice question

Crude oil is a naturally occurring source of hydrocarbons that serve as fuels.
(a(i))[1]

State the name of the process in which long-chain hydrocarbons are split into shorter-chain hydrocarbons.

(a(ii))[1]

Give one reason why hydrocarbons with low relative molecular mass, $M_r$, are suitable for use as fuels.

(a(iii))[1]

When hydrocarbons undergo incomplete combustion, carbon monoxide, $\text{CO}$, may be released into the atmosphere. Write an equation to show the formation of $\text{CO}$ from the incomplete combustion of butene, $\text{C}_4\text{H}_8$.

(a(iv))[2]

Identify an analytical technique that can be used to monitor the levels of $\text{CO}$ in the atmosphere. Describe how this analytical technique may be used to monitor the levels of $\text{CO}$.

(b(i))[2]

Construct the equation for the complete combustion of thiophene, $\text{C}_4\text{H}_4\text{S(l)}$. Show state symbols in your answer.

(b(ii))[2]

A student carries out an experiment to determine the enthalpy change of combustion of $\text{C}_4\text{H}_4\text{S(l)}$. Explain what is meant by the term enthalpy change of combustion.

(b(iii))[2]

The student uses the apparatus shown in the experiment. Calculate the heat energy released, in J, by the reaction. Assume that $4.18\,\text{J}$ of heat energy raises the temperature of $1.0\,\text{cm}^3$ of water by $1.0\,^\circ\text{C}$. Assume no heat is lost to the surroundings.

(b(iv))[2]

The student used $0.63\,\text{g}$ of $\text{C}_4\text{H}_4\text{S(l)}$ in the experiment. Calculate the enthalpy change of combustion of thiophene, $\Delta H_c(\text{C}_4\text{H}_4\text{S(l)})$. Give a sign in your answer.

(iii)[2]

The student uses the apparatus below in the experiment. Calculate the heat energy released, in J, by the reaction. Assume that $4.18\,\text{J}$ of heat energy increases the temperature of $1.0\,\text{cm}^3$ of water by $1.0\,^\circ\text{C}$. Assume no heat is lost to the surroundings.

(iv)[2]

The student used $0.63\,\text{g}$ of $\text{C}_4\text{H}_4\text{S(l)}$ in the experiment. Calculate the enthalpy change of combustion of thiophene, $\Delta H_c(\text{C}_4\text{H}_4\text{S(l)})$. Give a sign in your answer.

Worked solution & mark scheme

This 17-mark question has a full step-by-step worked solution and mark scheme. One marking point: The process is cracking.

  • Full mark scheme, point by point
  • Step-by-step worked solution
  • Write your answer & get it marked instantly by AI