All Free Chemistry MCQs with Answers

• A. C3 - C5 alkanes
• B. C15 - C20 alkanes
• C. C11 - C15 alkanes
• D. C7 - C9 alkanes

Explanation: C7-C9 alkanes: This range of alkanes is the ideal range for use in gasoline.

• A. Methane
• B. Ethane
• C. Butane
• D. Nitrogen

Explanation: Natural gas has Methane and ethane contributing to large portions with Methane being 90%, approximately, and ethane, up to 5%.

• A. CnH2n=2
• B. CnH2n
• C. CnH2n-1
• D. CnCH2n-2

Explanation: Option B shows the general formula of cycloalkane, n Is number of carbon is ring

• A. CnH2n+2
• B. CnH2n
• C. CnH2n - 1
• D. CnH2n - 2

Explanation: It is because cycloalkane has the same generic formula as the alkenes which is CnH2n.

• A. 2, 3 - tetramethyl butane
• B. 2, 2, 3, 3 - tetramethyl pentane
• C. 3, 3, 4, 4 - tetramethyl butane
• D. 3, 4 - bis (dimethyl butane)

Explanation: The longest carbon chain in the compound above is of five carbons as shown in the figure below, hence the correct option must have a…

• A. Isobutane
• B. Pentane
• C. Neo- pentane
• D. Isopentane

Explanation: Option C: Neo-pentane (CH3-C(CH3)3) does not have secondary or tertiary hydrogens.

• A. 80%
• B. 5%
• C. 65%
• D. 20%

Explanation: Gasoline produced by fractional distillation is 20% .

• A. Reforming
• B. Distillation
• C. Cracking
• D. Decomposition

Explanation: Reforming is a process in which hydrocarbons are converted into more branched or cyclic hydrocarbons by rearranging the carbon-carbon…

• A. Cracking
• B. Reforming
• C. Decomposition
• D. Isomerisation

Explanation: Fuels with a higher octane number can be produced by reforming. Reforming is a refining process used in the petroleum industry to increase…

• A. 100
• B. 95
• C. 9
• D. 89

Explanation: The octane number is a measure of a fuel's ability to resist knocking or detonation during combustion in an internal combustion engine.

• A. Reduction reaction
• B. Kolbe's reaction
• C. Clemmensen Reaction
• D. Hydrogenolysis

Explanation: OPTION A: Reduction reactions produce alkanes with unsymmetrical carbon chains, not symmetrical alkanes.OPTION B: Kolbe's Electrolysis…

• A. 0.8
• B. 0.85
• C. 0.7
• D. 0.98

Explanation: Natural gas typically contains about 75-90% methane. So, the correct answer would be 0.85.

• A. CO2 & H2O
• B. CO & H2O
• C. CO2 & H2
• D. CH3OH

Explanation: Catalytic oxidation of lower alkanes takes place in the presence of a metallic catalyst, for example, Cu, at high temperature and…

• A. Reforming
• B. Cracking
• C. Isomers
• D. Decomposition

Explanation: Reforming is a catalytic process in which straight- chain molecules are converted to branched forms. Hence, option A is correct

• A. 0
• B. 100
• C. 40
• D. 98

Explanation: If there is pure n-heptane, then its octane number is 0. n-heptane has zero octane number because of very poor knock resistance.

• A. Decrease the boiling point
• B. Prevent heating
• C. Prevent freezing of fuel
• D. Prevent knocking

Explanation: Organic lead (tetraethyl lead; TEL) is used as an antiknock agent in gasoline and jet fuels. It increases the octane number of the fuel.

• A. Tetramethyl lead
• B. Tetraethyl lead
• C. Iso-octane
• D. All of these

Explanation: Option A is incorrect as tetramethyl lead doesn't have anti-knocking properties.

• A. C- C
• B. C-H
• C. Both C-C and C-H
• D. C-0

Explanation: Cracking is the process whereby complex organic molecules such as long-chain hydrocarbons are broken down into simpler molecules such as…

• A. C-C
• B. C-H
• C. Both C-C and C-H
• D. C-O

Explanation: The primary types of bonds that are broken during cracking are C-C bonds.

• A. Cracking
• B. Hydrolysis
• C. Oxidation
• D. Distillation

Explanation: Cracking is the process in which long chain hydrocarbons (in liquid/solid state) are broken into short chain, more useful hydrocarbons…