Hydrocarbons Chapter-Wise Test 1

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Which hydrocarbon has a higher boiling point than its straight-chain isomer with the same molecular formula \( \ce{C5H12} \)?

Straight-chain pentane has a higher boiling point than branched isomers like 2,2-dimethylpropane due to greater surface area and stronger van der Waals forces.

Pentane
2-Methylbutane
2,2-Dimethylpropane
Cyclopentane
1

Which hydrocarbon produces 4 moles of \( \ce{CO2} \) and 5 moles of \( \ce{H2O} \) per mole upon complete combustion?

For \( \ce{C4H10} \) (butane): \( \ce{C4H10 + 13/2 O2 -> 4CO2 + 5H2O} \), producing 4 \( \ce{CO2} \) and 5 \( \ce{H2O} \).

\( \ce{C4H10} \)
\( \ce{C5H12} \)
\( \ce{C3H8} \)
\( \ce{C4H8} \)
1

Which hydrocarbon with 10 carbon atoms has the maximum possible branching and the lowest boiling point among its isomers?

For \( \ce{C10H22} \), 2,2,3,3-tetramethylhexane has four methyl branches, the most compact structure, lowering its boiling point the most.

Decane
2-Methylnonane
2,2-Dimethylnonane
2,2,3,3-Tetramethylhexane
4

Which hydrocarbon has the molecular formula \( \ce{C4H8} \)?

Butene (\( \ce{CH2=CH-CH2-CH3} \)) is an alkene with the formula \( \ce{C4H8} \), fitting \( \ce{C_nH_{2n}} \).

Butane
Propane
Pentane
Butene
4

What is the bond angle between carbon atoms in benzene?

Benzene has a planar hexagonal ring with \( sp^2 \) hybridized carbons, resulting in bond angles of 120°.

109.5°
90°
120°
180°
3

Which hydrocarbon with 4 carbon atoms has the maximum number of hydrogen atoms possible?

Butane (\( \ce{C4H10} \)), a saturated alkane, has 10 hydrogens, the maximum for 4 carbons, compared to unsaturated hydrocarbons like butene.

Butene
Butane
Cyclobutane
Butyne
2

What is the product of complete combustion of \( \ce{C4H10} \)?

Complete combustion of hydrocarbons produces carbon dioxide and water. For \( \ce{C4H10} \) (butane): \( \ce{2C4H10 + 13O2 -> 8CO2 + 10H2O} \).

\( \ce{CO + H2} \)
\( \ce{CO2 + H2O} \)
\( \ce{C + H2O} \)
\( \ce{CO2 + H2} \)
2

What is the general formula for alkanes?

Alkanes are saturated hydrocarbons with single bonds, and their general formula is \( \ce{C_nH_{2n+2}} \), where \( n \) is the number of carbon atoms.

\( \ce{C_nH_{2n+2}} \)
\( \ce{C_nH_{2n}} \)
\( \ce{C_nH_{2n-2}} \)
\( \ce{C_nH_n} \)
1

Which hydrocarbon with molecular formula \( \ce{C8H12} \) contains three degrees of unsaturation and no rings?

Octatriyne (\( \ce{CH#C-C#C-C#C-CH2-CH3} \)) has three triple bonds, giving three degrees of unsaturation, fitting \( \ce{C8H12} \).

Octene
Octatriyne
Cyclooctadiene
Ethylbenzene
2

Which hydrocarbon with 5 carbon atoms requires the least amount of oxygen per mole for complete combustion?

Cyclopentane (\( \ce{C5H10} \)) requires 15/2 \( \ce{O2} \) (\( \ce{C5H10 + 15/2 O2 -> 5CO2 + 5H2O} \)), less than pentane’s 8 \( \ce{O2} \).

Pentane
Pentene
Cyclopentane
Pentyne
3

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