(C) Different fractions of crude oil in petroleum industry
(III) Distillation at reduced pressure
(D) Chloroform-Aniline mixture
(IV) Steam distillation
Choose the correct answer from the options given below:
A.(A)-(IV), (B)-(III), (C)-(II), (D)-(I)
B.(A)-(I), (B)-(II), (C)-(III), (D)-(IV)
C.(A)-(III), (B)-(IV), (C)-(I), (D)-(II)
D.(A)-(II), (B)-(I), (C)-(IV), (D)-(III)
Solution & Explanation
### Core Logic
Evaluating standard NCERT laboratory purification matches:
- **(A) Aniline from aniline-water mixture:** Aniline is steam volatile and immiscible with water, so it is separated via **Steam distillation (IV)**.
- **(B) Glycerol from spent-lye in soap industry:** Glycerol decomposes at or below its boiling point, hence it is separated via **Distillation at reduced pressure (III)**.
- **(C) Different fractions of crude oil:** Separated using their small differences in boiling points via **Fractional distillation (II)**.
- **(D) Chloroform-Aniline mixture:** Separated due to a substantial boiling point difference via **Simple distillation (I)**.
### Pattern Recognition
Match key words directly: Glycerol/spent-lye always links to reduced pressure (vacuum distillation). Crude oil always couples to fractional columns. Aniline + water implies steam injection.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 11 Chemistry: Some Basic Principles of Organic Chemistry
### Core Logic
Let us review the chemical basis for each qualitative test:
* **A. Sodium bicarbonate (textNaHCO_3$\text{NaHCO}_3$) solution**: Carboxylic acids are sufficiently acidic to decompose textNaHCO_3$\text{NaHCO}_3$, liberating carbon dioxide gas observed as vigorous effervescence. Therefore, textA rightarrow textII$\text{A} \rightarrow \text{II}$.
* **B. Neutral ferric chloride (textFeCl_3$\text{FeCl}_3$)**: Phenols react with neutral textFeCl_3$\text{FeCl}_3$ solution to form characteristic deeply colored violet coordination complexes. Therefore, textB rightarrow textIII$\text{B} \rightarrow \text{III}$.
* **C. Ceric ammonium nitrate (CAN)**: Alcohols react with CAN reagent to cause a distinct color shift to deep dark red due to complexation. Therefore, textC rightarrow textIV$\text{C} \rightarrow \text{IV}$.
* **D. Alkaline textKMnO_4$\text{KMnO}_4$ (Baeyer's Reagent)**: Reacts readily via syn-hydroxylation across carbon-carbon double/triple bonds, resulting in decolored solutions alongside brown textMnO_2$\text{MnO}_2$ precipitates. This detects unsaturation. Therefore, textD rightarrow textI$\text{D} \rightarrow \text{I}$.
### Step 1: Assembly
Combining the validated relationships gives:
textA-II, B-III, C-IV, D-I$$\text{A-II, B-III, C-IV, D-I}$$
This maps perfectly to Option (1).
### Pattern Recognition
Baeyer's test (alkaline textKMnO_4$\text{KMnO}_4$) always tests for alkenes/alkynes. textNaHCO_3$\text{NaHCO}_3$ is unique for acidic groups like carboxylic acids. Matching these two reliable pairs isolates the correct option without needing to review the entire table.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques
Class 12 Chemistry: Alcohols, Phenols and Ethers
Given below are two statements:
Statement (I): In partition chromatography, stationary phase is thin film of liquid present in the inert support.
Statement (II): In paper chromatography, the material of paper acts as a stationary phase.
In the light of the above statements, choose the correct answer from the options given below:
A. Both Statement I and Statement II are false
B. Statement I is true but Statement II is false
C. Both Statement I and Statement II are true
D. Statement I is false but Statement II is true
Solution
### Core Logic
Statement I is true: In partition chromatography, the stationary phase is indeed a thin film of liquid held on the surface of an inert solid support.
Statement II is false: In paper chromatography, the water molecules trapped inside the cellulose network of the paper act as the stationary phase, not the paper material itself.
### Pattern Recognition
Remember that paper chromatography is a type of partition chromatography where moisture content (water) adsorbed on the paper serves as the stationary liquid phase.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques
Q38jee_main_2025_29_jan_eveningSigma and Pi Bond Counting
Total number of sigma (sigma)$(sigma)$ and pi(pi)$pi(pi)$ bonds respectively present in hex-1-en-4-yne are:
A. 13 and 3
B. 11 and 3
C. 3 and 13
D. 14 and 3
Solution
### Core Logic
The structural formula of hex-1-en-4-yne is given by:
CH_2 = CH - CH_2 - C equiv C - CH_3$$CH_2 = CH - CH_2 - C equiv C - CH_3$$
Let's count the chemical bonds chronologically:
* Number of C-H$C-H$sigma$sigma$ bonds = 2 + 1 + 2 + 3 = 8$2 + 1 + 2 + 3 = 8$
* Number of C-C$C-C$sigma$sigma$ bonds = 5$5$
Total sigma$sigma$ bonds = 8 + 5 = 13$8 + 5 = 13$.
Sigma and Pi Bond Counting diagram for Q38 - JEE Main 2025 Evening
* Number of pi$pi$ bonds: 1$1$ from double bond + 2$2$ from triple bond = 3$3$pi$pi$ bonds.
### Pattern Recognition
Every single bond is 1sigma$1sigma$, every double bond contains 1sigma + 1pi$1sigma + 1pi$, and every triple bond contains 1sigma + 2pi$1sigma + 2pi$.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques
Q49jee_main_2025_29_jan_eveningQuantitative Estimation of Sulphur
In the sulphur estimation, 0.20text g$0.20\text{ g}$ of a pure organic compound gave 0.40text g$0.40\text{ g}$ of barium sulphate.
The percentage of sulphur in the compound is x times 10^-1\%$x \times 10^{-1}\%$, where x$x$ = ________.
(Molar mass: O=16$O=16$, S=32$S=32$, Ba=137text in g mol^-1$Ba=137\text{ in g mol}^{-1}$)
Numerical Answer.Answer: 275 to 275
Solution
### Related Formula
%S = frac32233 times fractextMass of BaSO_4textMass of organic compound times 100$$%S = \frac{32}{233} \times \frac{\text{Mass of } BaSO_4}{\text{Mass of organic compound}} \times 100$$
### Core Logic
Let's substitute the given values into the formula:
textMass of BaSO_4 = 0.40text g$$\text{Mass of } BaSO_4 = 0.40\text{ g}$$textMass of organic compound = 0.20text g$$\text{Mass of organic compound} = 0.20\text{ g}$$textMolar mass of BaSO_4 = 137 + 32 + (4 times 16) = 233text g/mol$$\text{Molar mass of } BaSO_4 = 137 + 32 + (4 \times 16) = 233\text{ g/mol}$$%S = frac32233 times frac0.400.20 times 100 = frac32 times 2 times 100233 approx 27.468%$$%S = \frac{32}{233} \times \frac{0.40}{0.20} \times 100 = \frac{32 \times 2 \times 100}{233} approx 27.468%$$
### Step 1: Match with the Question Layout
Rounding to the standard value given in the official key:
%S = 27.5% = 275 times 10^-1% implies x = 275$$%S = 27.5% = 275 \times 10^{-1}% implies x = 275$$
### Pattern Recognition
Carius method calculations depend heavily on standard conversion factors. The constant factor for sulphur gravimetry is frac32233$\frac{32}{233}$.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques
The correct order of stability of following carbocations is :
The images show different structural models labeled A, B, C, and D for evaluating stability variations.
A
The images show different structural models labeled A, B, C, and D for evaluating stability variations.
B
The images show different structural models labeled A, B, C, and D for evaluating stability variations.
C
The images show different structural models labeled A, B, C, and D for evaluating stability variations.
D
### Core Logic
To evaluate carbocation stability, apply the priority rules: Aromaticity > Resonance > Hyperconjugation.
- **C:** Represents a cyclopropenyl cation derivative which achieves full aromatic stabilization due to its planar cyclic conjugated system satisfying Huckel's rule (2pi$2\pi$ electrons). This makes it the most stable.
- **A:** Stabilized by extended resonance from multiple phenyl groups.
- **B:** Contains fewer phenyl rings participating in active cross-conjugation relative to A.
- **D:** Stabilized solely by simple aliphatic hyperconjugation, making it the least stable.
Visual alignment chart:
The images show different structural models labeled A, B, C, and D for evaluating stability variations.
Hence, the correct stability hierarchy is:
mathrmC > mathrmA > mathrmB > mathrmD$$\mathrm{C} > \mathrm{A} > \mathrm{B} > \mathrm{D}$$
### Pattern Recognition
Sees: Mixed aromatic, benzylic, and aliphatic carbocations.
Shortcut: Isolate the cyclopropenyl system as an aromatic champion to confidently lead the sequence.
### Evaluation Rubric / Model Answer
null
### Chapter Mix
Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques
More Some Basic Principles of Organic Chemistry Questions — jee_main_2025_04_april_evening
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