QUESTION 145 (5 marks)
A two-step synthesis converts ethane to ethylamine through chloroethane. Only the monosubstitution product is considered in the first step. Excess ammonia is used in the second step.
(a) Write a balanced equation for the first step and state the required light condition. [2 marks]
(b) Write a balanced equation for reaction of chloroethane with ammonia, including the ammonium salt. [2 marks]
(c) Classify the second step. [1 marks]
Practice marking scheme
Answer
under UV light. . The second step is substitution.
Working
UV light enables alkane chlorination; one H is replaced by Cl in the specified monosubstitution model. Chloroethane reacts with excess ammonia on heating. One ammonia supplies the amino group and another accepts a proton to form ammonium chloride. The Cl-bearing group is replaced by an amino group.
Marking criteria
- Writes the balanced monosubstitution chlorination equation. [1 mark]
- States UV light for the first step. [1 mark]
- Gives ethylamine as the organic product of the second step. [1 mark]
- Balances the second step with two NH₃ and NH₄Cl. [1 mark]
- Classifies the second step as substitution. [1 mark]
Practice question aligned to the current QCAA syllabus; review the worked solution and marking criteria.
View the QCAA syllabusCompare your working with the guide above.