Organic Chemistry – Some Basic Principles and Techniques Chapter-Wise Test 10

Correct answer Carries: 4.

Wrong Answer Carries: -1.

A mixture of two liquids with boiling points 75°C and 90°C is separated efficiently on a large scale using which technique?

A 15°C difference (< 25°C) requires fractional distillation for efficient large-scale separation due to close boiling points.

Simple distillation
Differential extraction
Fractional distillation
Chromatography
3

Which purification technique is most suitable for separating a mixture of \( \ce{CHCl3} \) (b.p. 61°C) and \( \ce{CH3COCH3} \) (b.p. 56°C)?

Fractional distillation separates liquids with close boiling points (difference < 25°C) using a fractionating column.

Simple distillation
Fractional distillation
Sublimation
Crystallization
2

How many structural isomers are possible for \( \ce{C5H12} \)?

\( \ce{C5H12} \) (pentane) has three structural isomers: n-pentane (\( \ce{CH3CH2CH2CH2CH3} \)), 2-methylbutane (\( \ce{CH3CH(CH3)CH2CH3} \)), and 2,2-dimethylpropane (\( \ce{C(CH3)4} \)).

2
3
4
5
2

A hydrocarbon with 8 \( \sigma \) bonds and 2 \( \pi \) bonds undergoes complete combustion to produce 3 moles of \( \ce{CO2} \) per mole of compound. What is its molecular formula?

3 carbons (from 3 \( \ce{CO2} \)). \( \ce{CH3C#CH} \) has 8 \( \sigma \) (6 C-H, 1 C-C, 1 from C≡C) and 2 \( \pi \) (C≡C), and is \( \ce{C3H4} \), producing 3 \( \ce{CO2} \) on combustion.

\( \ce{C4H6} \)
\( \ce{C3H4} \)
\( \ce{C3H6} \)
\( \ce{C4H8} \)
2

Which technique is used to separate colored components of a mixture based on their \( R_f \) values?

Paper chromatography separates components based on their retention factor (\( R_f \)), often used for colored substances like inks or dyes.

Distillation
Sublimation
Fractional distillation
Paper chromatography
4

Which carbon in \( \ce{CH2=CHCH2OH} \) is \( sp^3 \) hybridized?

In \( \ce{CH2=CHCH2OH} \), the third carbon (\( \ce{CH2OH} \)) has four single bonds (to C, O, and two H), indicating \( sp^3 \) hybridization.

First carbon
Second carbon
Third carbon
All carbons
3

Which intermediate is least stable when formed from \( \ce{CH3CH2CH2CH3} \) via homolytic cleavage?

Homolytic cleavage at \( \ce{CH3-CH2} \) forms \( \ce{CH3.} \) (primary radical), less stable than \( \ce{CH3CH2CH2CH2.} \) (primary) or secondary radicals due to minimal hyperconjugation.

\( \ce{CH3CH2CH2CH2.} \)
\( \ce{CH3.} \)
\( \ce{CH3CH2CH2.} \)
\( \ce{CH3CH2.} \)
2

In the Carius method, 0.6 g of a compound gave 0.717 g of \( \ce{AgI} \). What is the percentage of iodine?

Molar mass of \( \ce{AgI} = 235 \) g/mol, I = 127 g/mol. Mass of I = \( \frac{127}{235} \times 0.717 \approx 0.387 \) g. Percentage = \( \frac{0.387}{0.6} \times 100 \approx 64.5\% \), which rounds to 64%.

62%
64%
66%
68%
2

Which species is least likely to act as an electrophile in a reaction with \( \ce{CH3CH=CH2} \)?

\( \ce{CH3^-} \) is electron-rich (carbanion), making it a nucleophile, not an electrophile, unlike the others which are electron-deficient.

\( \ce{H+} \)
\( \ce{Cl+} \)
\( \ce{NO2+} \)
\( \ce{CH3^-} \)
4

In Dumas method, 0.4 g of a compound gave 60 mL of \( \ce{N2} \) at STP. What is the percentage of nitrogen?

Volume of \( \ce{N2} \) at STP = 60 mL. Mass of N = \( \frac{28}{22400} \times 60 = 0.075 \) g. Percentage = \( \frac{0.075}{0.4} \times 100 = 18.75\% \).

15%
17.5%
20%
18.75%
4

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