Organic Chemistry – Some Basic Principles and Techniques Chapter-Wise Test 2

Correct answer Carries: 4.

Wrong Answer Carries: -1.

In the Dumas method, 0.35 g of a compound gave 90 mL of \( \ce{N2} \) at STP, and in Carius method, 0.35 g gave 0.574 g of \( \ce{AgBr} \). What is the percentage of nitrogen?

Mass of N = \( \frac{28}{22400} \times 90 = 0.1125 \) g. Percentage = \( \frac{0.1125}{0.35} \times 100 = 32.14\% \approx 32\% \). Carius data is for bromine, not relevant here.

31%
33%
34%
32%
4

Which reagent is used in the Carius method to oxidize the organic compound?

Fuming nitric acid (\( \ce{HNO3} \)) is used in the Carius method to oxidize the compound and convert halogens to their respective acids.

\( \ce{H2SO4} \)
\( \ce{HCl} \)
\( \ce{HNO3} \)
\( \ce{NaOH} \)
3

Which purification method would fail to separate a mixture of two organic solids with identical sublimation temperatures but different solubilities in water?

Sublimation relies on sublimation temperature differences, ineffective here. Crystallization or extraction using water solubility would work instead.

Crystallization
Differential extraction
Chromatography
Sublimation
4

In Lassaigne’s test, the presence of sulphur is confirmed by the formation of a violet color with which reagent?

Sulphur forms \( \ce{Na2S} \) in Lassaigne’s test, which reacts with sodium nitroprusside to give a violet-colored complex, \( \ce{Na4[Fe(CN)5NOS]} \).

Sodium nitroprusside
Ferric chloride
Lead acetate
Silver nitrate
1

A hydrocarbon with 9 \( \sigma \) bonds produces 5 moles of \( \ce{CO2} \) per mole upon combustion. What is its molecular formula?

5 carbons (from 5 \( \ce{CO2} \)). \( \ce{CH3CH2CH2CH2CH3} \) (pentane) has 9 \( \sigma \) (8 C-H, 1 C-C from single bonds), no \( \pi \), and fits \( \ce{C5H12} \).

\( \ce{C5H10} \)
\( \ce{C5H12} \)
\( \ce{C4H8} \)
\( \ce{C5H8} \)
2

Which of the following is a homologous series?

A homologous series has compounds with the same functional group differing by \( \ce{-CH2-} \). Alkanes (e.g., \( \ce{CH4, C2H6, C3H8} \)) fit this definition.

Alkenes and alkynes
Alkanes
Alcohols and aldehydes
Aromatic compounds
2

An organic compound with \( \ce{C5H8} \) has a degree of unsaturation of 2. Which functional group combination could it contain?

Degree of unsaturation = \( \frac{2C + 2 - H}{2} = \frac{12 - 8}{2} = 2 \). \( \ce{CH3CH2C#CCH3} \) has one triple bond (2 units), fitting \( \ce{C5H8} \).

Two double bonds
One triple bond
One double bond and one ring
Two rings
2

Which carbon in \( \ce{CH3CH2C(=O)CH2CH3} \) is most stabilized by the hyperconjugation effect if it forms a carbocation?

In \( \ce{CH3CH2C(=O)CH2CH3} \), the carbon in \( \ce{CH2} \) adjacent to \( \ce{C=O} \) (second carbon) forms \( \ce{CH3CH+CH2C(=O)CH3} \), stabilized by hyperconjugation from \( \ce{CH3} \).

First carbon
Second carbon
Carbonyl carbon
Fourth carbon
2

Which compound has the functional group \( \ce{-CHO} \)?

The \( \ce{-CHO} \) group is characteristic of aldehydes. \( \ce{CH3CH2CHO} \) (propanal) contains this group.

\( \ce{CH3CH2CHO} \)
\( \ce{CH3COCH3} \)
\( \ce{CH3CH2OH} \)
\( \ce{CH3COOH} \)
1

What is the total number of \( \sigma \) bonds in \( \ce{CH3CH2CH=CH2} \)?

In \( \ce{CH3CH2CH=CH2} \) (but-1-ene), there are 11 \( \sigma \) bonds: 8 C-H, 2 C-C, 1 from C=C.

11
10
12
9
1

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