Hydrocarbons Chapter-Wise Test 2

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Which group deactivates the benzene ring towards electrophilic substitution?

The \( -\ce{COOH} \) group withdraws electrons due to its strong -I effect, deactivating the benzene ring and directing substitution to the meta position.

\( -\ce{CH3} \)
\( -\ce{COOH} \)
\( -\ce{NH2} \)
\( -\ce{OCH3} \)
2

Which hydrocarbon has the lowest carbon-to-hydrogen ratio among the following?

Octane (\( \ce{C8H18} \)) has a C:H ratio of 8:18 (0.44), lower than benzene’s 1:1 or butyne’s 4:6 (0.67).

\( \ce{C6H6} \)
\( \ce{C4H6} \)
\( \ce{C5H10} \)
\( \ce{C8H18} \)
4

What type of bonds form the tetrahedral structure of methane?

The tetrahedral structure of methane is due to sigma bonds formed by the overlap of \( sp^3 \) hybrid orbitals of carbon with \( s \) orbitals of hydrogen.

Pi bonds
Double bonds
Triple bonds
Sigma bonds
4

Which hydrocarbon has the molecular formula \( \ce{C5H10} \)?

Pentene (\( \ce{CH2=CH-CH2-CH2-CH3} \)) is an alkene with the formula \( \ce{C5H10} \), fitting \( \ce{C_nH_{2n}} \).

Pentane
Hexane
Pentene
Butene
3

What is the effect of increasing molecular mass on the melting point of alkanes?

Increasing molecular mass in alkanes enhances van der Waals forces, raising the melting point.

Decreases
No effect
Fluctuates
Increases
4

Which hydrocarbon produces 8 moles of \( \ce{CO2} \) per mole upon complete combustion and has 8 carbon atoms?

For \( \ce{C8H18} \) (octane): \( \ce{C8H18 + 25/2 O2 -> 8CO2 + 9H2O} \), producing 8 moles of \( \ce{CO2} \).

\( \ce{C8H16} \)
\( \ce{C8H14} \)
\( \ce{C8H10} \)
\( \ce{C8H18} \)
4

Which hydrocarbon with 7 carbon atoms has three degrees of unsaturation and a ring structure?

Toluene (\( \ce{C7H8} \)) has a benzene ring (3 pi bonds) and one additional carbon, giving three degrees of unsaturation.

Heptane
Cycloheptene
Heptadiyne
Toluene
4

Which compound is an example of an aromatic hydrocarbon?

Aromatic hydrocarbons have a cyclic structure with delocalized π electrons. Benzene (\( \ce{C6H6} \)) fits this description.

\( \ce{CH4} \)
\( \ce{C6H6} \)
\( \ce{C2H4} \)
\( \ce{C3H8} \)
2

Which hydrocarbon is found in petroleum gas?

Petroleum gas, obtained from oil wells, contains low molecular weight alkanes like ethane (\( \ce{C2H6} \)).

Ethane
Benzene
Toluene
Pentene
1

What is the common name of \( \ce{CH3CH2CH3} \)?

The compound \( \ce{CH3CH2CH3} \) is a three-carbon alkane, commonly known as propane.

Butane
Ethane
Propane
Methane
3

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