1

### AIPMT 2015 Cancelled Paper

In Duma's method for estimation of nitrogen, 0.25 g of an organic compound gave 40 mL of nitrogen collected at 300 K temperature and 725 mm pressure. If the aqueous tension at 300 K is 25 mm, the percentage of nitrogen in the compound is
A
16.75
B
15.76
C
17.36
D
18.20

## Explanation

Wt. of organic substance = 0.25 g

V1 = 40 mL, T1 = 300 K

P1 = 725 – 25 = 700 mm of Hg

P2 = 760 mm of Hg (at STP)

T2 = 273 K

${{{P_1}{V_1}} \over {{T_1}}} = {{{P_2}{V_2}} \over {{T_2}}}$

V2 = ${{700 \times 40 \times 273} \over {300 \times 760}}$ = 33.52 mL

Percentage of nitrogen

= ${{28 \times 33.52 \times 100} \over {22400 \times 0.25}}$

= 16.76%
2

### AIPMT 2015 Cancelled Paper

Which of the following is the most correct electron displacement for a nucleophilic reaction to take place?
A B C D ## Explanation

$\pi$ bond is transferred after leaving Cl then nucleophile will attack a stable carbocation. 3

### AIPMT 2015 Cancelled Paper

Given : Which of the given compounds can exhibit tautomerism?
A
II and III
B
I, II and III
C
I and II
D
I and III

## Explanation In first two cases $\alpha$-H participates in tautomerism.

And in third case, $\gamma$-H participate in tautomerism.
4

### AIPMT 2015 Cancelled Paper

The total number of $\pi$-bond electrons in the following structure is A
12
B
16
C
4
D
8

## Explanation

No. of double bonds = 4

No. of $\pi$ bond electrons

= 2 × no. of double bond

= 2 × 4 = 8