ECAT Chemistry — Hydrocarbons
Hydrocarbons is part of the Chemistry section of the UET ECAT (30 of the 100 MCQs). It breaks into 3 subtopics, and we hold 26 ECAT-pattern practice MCQs on it, each with a written explanation. Tap a subtopic below to practise just that.
Subtopics (3)
How Hydrocarbons is tested
Across the 7 ECAT past papers on ParhaiKrlo, Hydrocarbons accounts for 10 questions. It appears in 6 of them, about 1.7 questions a paper. The heaviest was ECAT Past Paper 06, with 3 questions, and the most recent is ECAT Past Paper 07, with 1.
| Paper | Questions |
|---|---|
| ECAT Past Paper 07 | 1 |
| ECAT Past Paper 06 | 3 |
| ECAT Past Paper 05 | 1 |
| ECAT Past Paper 04 | 2 |
| ECAT Past Paper 03 | 2 |
| ECAT Past Paper 02 | 1 |
Hydrocarbons MCQs from the ECAT past papers
Try each one before opening the answer. Each comes with a short explanation.
- Q1 · ECAT Past Paper 07 · Hydrocarbons
Alkanes are less reactive than alkenes because:
- A.Electrons are tightly held in the sigma bonds of alkanes
- B.The pi-electron cloud in alkenes lies away from the nuclei, making them more reactive
- C.Pi bonds make alkenes reactive towards electrophilic reagents
- D.All of the above
Show answer
Answer: D. All of the above — Alkanes have only strong σ bonds; alkenes have an exposed π cloud that attracts electrophiles.
- Q2 · ECAT Past Paper 06 · Hydrocarbons
Alkanes (paraffins) are made up of:
- A.Carbon, hydrogen and oxygen only
- B.Carbon, hydrogen and sulphur only
- C.Carbon, hydrogen and nitrogen only
- D.Carbon and hydrogen only
Show answer
Answer: D. Carbon and hydrogen only — Alkanes are saturated hydrocarbons: C and H only.
- Q3 · ECAT Past Paper 05 · Hydrocarbons
In the reaction between chlorine and methane in UV light, a propagation step is:
- A.CH₄ + Cl• → CH₃• + HCl
- B.CH₄ + Cl• → CH₃Cl + H•
- C.CH₄ + Cl• → CH₃Cl
- D.H• + Cl₂ → Cl• + HCl
Show answer
Answer: A. CH₄ + Cl• → CH₃• + HCl — A chlorine radical abstracts H from methane, giving a methyl radical and HCl (and the radical chain continues).