Hydrocarbons Chapter-Wise Test 12

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Which hydrocarbon class has the highest carbon-to-hydrogen ratio?

Alkynes (\( \ce{C_nH_{2n-2}} \)) have the highest C:H ratio (e.g., \( \ce{C2H2} \) is 1:1) compared to alkanes (\( \ce{C_nH_{2n+2}} \)) or alkenes (\( \ce{C_nH_{2n}} \)).

Alkynes
Alkanes
Alkenes
Cycloalkanes
1

A hydrocarbon with 7 carbon atoms and 12 hydrogen atoms has one ring. What is its IUPAC name?

\( \ce{C7H12} \) with one ring and one degree of unsaturation suggests cycloheptene, a seven-membered ring with one double bond.

Cycloheptane
Cycloheptene
Heptadiyne
Toluene
1

Which hydrocarbon is used as a domestic fuel with the least pollution?

LPG, primarily butane (\( \ce{C4H10} \)), is used as a domestic fuel and produces the least pollution compared to kerosene or coal gas.

\( \ce{CH4} \)
\( \ce{C6H6} \)
\( \ce{C3H8} \)
\( \ce{C4H10} \)
4

Which hydrocarbon would require the least amount of oxygen per carbon atom for complete combustion?

Benzene (\( \ce{C6H6} \)) requires 15/2 \( \ce{O2} \) for 6 carbons (1.25 \( \ce{O2} \)/C), less than alkanes like \( \ce{C6H14} \) (19/2 \( \ce{O2} \), 1.58 \( \ce{O2} \)/C).

\( \ce{C5H12} \)
\( \ce{C6H14} \)
\( \ce{C4H10} \)
\( \ce{C6H6} \)
4

What is the hybridization of carbon atoms in alkanes?

In alkanes, carbon atoms form four single bonds, resulting in \( sp^3 \) hybridization, as seen in their tetrahedral structure.

\( sp^3 \)
\( sp^2 \)
\( sp \)
\( sp^3d \)
1

Which group activates the benzene ring towards electrophilic substitution?

The \( -\ce{NH2} \) group increases electron density on the benzene ring via resonance, activating it for electrophilic substitution.

\( -\ce{NO2} \)
\( -\ce{COOR} \)
\( -\ce{CHO} \)
\( -\ce{NH2} \)
4

Which hydrocarbon is a liquid at room temperature?

Hexane (\( \ce{C6H14} \)), with 6 carbons, is a liquid at room temperature (boiling point ~68°C), unlike lower alkanes which are gases.

\( \ce{CH4} \)
\( \ce{C2H6} \)
\( \ce{C4H10} \)
\( \ce{C6H14} \)
4

Which hydrocarbon has the molecular formula \( \ce{C3H4} \)?

Propyne (\( \ce{CH3C#CH} \)) is an alkyne with the formula \( \ce{C3H4} \), fitting \( \ce{C_nH_{2n-2}} \).

Propane
Propyne
Propene
Butane
2

What is the \( \ce{C-H} \) bond length in alkanes?

In alkanes, the \( \ce{C-H} \) bond length is 112 pm, formed by the overlap of \( sp^3 \) and \( s \) orbitals.

154 pm
112 pm
134 pm
120 pm
2

What is the effect of unsaturation on the reactivity of hydrocarbons?

Unsaturation (double or triple bonds) increases reactivity due to the presence of π bonds, which are more reactive than sigma bonds.

Decreases
No effect
Fluctuates
Increases
4

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