250+ TOP MCQs on Conventional Fuels and Answers

Automobile Engineering Multiple Choice Questions on “Conventional Fuels”.

1. How are hydrocarbons decomposed into smaller hydrocarbons?
a) By reforming
b) By refining
c) By cracking
d) By polymerization
Answer: c
Clarification: Hydrocarbons are decomposed into smaller hydrocarbons by cracking. Cracking consists of breaking down large complex hydrocarbon molecules into simpler compounds.

2. For SI engines which fuels are preferred?
a) Aromatics
b) Paraffin
c) Olefins
d) Napthenes
Answer: a
Clarification: For SI engines aromatic fuels are preferred. Aromatic compounds are ring structured. They have a benzene molecule as their central structure and also a general chemical formula is C_nH_2n-6.

3. For CI engines which fuels are preferred?
a) Napthenes
b) Paraffin
c) Olefins
d) Aromatics
Answer: b
Clarification: For CI engines paraffin fuels are preferred. The paraffin family consists of an open-chain structure with an attached branch. They are usually termed branched-chain paraffin.

4. Which molecular structure does the paraffin possess?
a) Chain saturated
b) Chain unsaturated
c) Ring saturated
d) Ring unsaturated
Answer: a
Clarification: The paraffin possesses a chain structure and is saturated in nature. In these hydrocarbons, the valency of all four carbon atoms is fully utilized by single bonds with hydrogen atoms.

5. Which of the following is the advantage of the gaseous fuel?
a) It can be stored easily
b) It can mix easily with air
c) It can displace more air from the engine
d) It can be stored, get mixed with air and can displace more air from the engine.
Answer: b
Clarification: The advantage of the gaseous fuel is that it can mix easily with air. Gaseous fuels are ideal fuels. They pose very few problems in using them in IC engines.

6. What is octane number of iso-octane?
a) 0
b) 30
c) 60
d) 100
Answer: d
Clarification: Iso-octane has octane number 100. The octane number fuel is defined as the percentage of iso-octane in a mixture of iso-octane and normal heptane by volume.

7. By which quantity is ignition quality of diesel fuel indicated?
a) Fire point
b) Flashpoint
c) Cetane point
d) Octane point
Answer: c
Clarification: Ignition quality of diesel fuel indicated by cetane point. Cetane number of a fuel is defined as the percentage of normal cetane in a mixture of normal cetane and α-methyl naphthalene by volume.

8. How is paraffin represented by?
a) C_nH_n
b) C_nH_2n
c) C_nH_2n+2
d) C_nH_2n-6
Answer: c
Clarification: The paraffin is represented by C_nH_2n+2. The normal paraffin hydrocarbons are of straight-chain molecular structure. Iso-butane has the same general chemical formula and molecular weight as butane.

9. What are the characteristics of good CI engine fuel?
a) High octane number
b) Very high cetane number
c) Short ignition lag
d) Short ignition lag, high cetane number, and high octane number
Answer: c
Clarification: Short ignition lags are the characteristics of good CI engine fuel. The CI engine fuel should be volatile in the operating range of temperature to produce good mixing and combustion.

10. How is the molecular structure of the straight-run gasoline changed?
a) By cracking
b) By reforming
c) By refining
d) By boiling
Answer: b
Clarification: The molecular structure of the straight-run gasoline is changed by reforming. Reforming is a cracking process which is used to convert the low antiknock quality gasoline into gasoline of higher octane rating.