Organic Chemistry – Some Basic Principles and Techniques Chapter-Wise Test 14

Correct answer Carries: 4.

Wrong Answer Carries: -1.

What is the shape of the carbon atom in \( \ce{CH3CH2CH2CHO} \) attached to the carbonyl group?

In \( \ce{CH3CH2CH2CHO} \), the carbonyl carbon (\( \ce{C=O} \)) has three sigma bonds and one pi bond, indicating \( sp^2 \) hybridization and a trigonal planar shape.

Tetrahedral
Linear
Trigonal planar
Bent
3

In the estimation of carbon and hydrogen, 0.15 g of a compound gave 0.135 g of \( \ce{H2O} \). What is the percentage of hydrogen?

Mass of H = \( \frac{2}{18} \times 0.135 = 0.015 \) g. Percentage = \( \frac{0.015}{0.15} \times 100 = 10\% \).

8%
9%
11%
10%
4

Which of the following carbocations is most stable due to hyperconjugation?

\( \ce{(CH3)2CH+} \) (secondary) is more stable than primary carbocations due to hyperconjugation with adjacent C-H bonds, but less stable than tertiary ones.

\( \ce{CH3+} \)
\( \ce{CH3CH2+} \)
\( \ce{(CH3)2CH+} \)
\( \ce{CH3CH2CH2+} \)
3

In the estimation of nitrogen by Dumas method, 0.4 g of a compound produces 84 mL of \( \ce{N2} \) at STP, and in Carius method, 0.4 g gives 0.382 g of \( \ce{AgCl} \). What is the percentage of nitrogen?

Mass of N = \( \frac{28}{22400} \times 84 = 0.105 \) g. Percentage = \( \frac{0.105}{0.4} \times 100 = 26.25\% \). (Carius data is a distractor for chlorine, not needed here.)

25%
26%
26.25%
27%
3

What is the total number of sigma bonds in \( \ce{CH2=CHCH2CH3} \)?

In \( \ce{CH2=CHCH2CH3} \) (but-1-ene), there are 11 \( \sigma \) bonds: 8 C-H, 2 C-C, 1 from C=C.

11
10
12
9
1

What is the total number of sigma bonds in \( \ce{CH3CH2C#CH} \)?

In \( \ce{CH3CH2C#CH} \) (but-1-yne), there are 9 \( \sigma \) bonds: 5 C-H, 2 C-C, 2 from C≡C.

9
8
10
7
1

Which of the following is a nucleophile?

\( \ce{CH3NH2} \) (methylamine) has a lone pair on nitrogen, making it an electron-rich nucleophile.

\( \ce{BCl3} \)
\( \ce{CH3CH2+} \)
\( \ce{NO2+} \)
\( \ce{CH3NH2} \)
4

Which type of intermediate is formed during the homolytic cleavage of \( \ce{Cl-Cl} \)?

Homolytic cleavage of \( \ce{Cl-Cl} \) produces two \( \ce{Cl.} \) radicals, each with an unpaired electron.

Carbocation
Free radical
Carbanion
Carbene
2

A mixture of two solids, one subliming at 60°C and the other melting at 120°C, is best separated by which technique?

Sublimation separates the solid that sublimes at 60°C from the one that melts at 120°C, exploiting the phase change difference.

Crystallization
Differential extraction
Sublimation
Chromatography
3

Which technique would be least effective for purifying a mixture of two solids, one of which sublimes at 50°C and the other decomposes at 200°C?

Sublimation would separate the sublimable solid effectively. Crystallization, requiring a solvent, is less suitable as it’s designed for soluble impurities, not thermal properties.

Crystallization
Sublimation
Differential extraction
Chromatography
1

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