Subject

Chemistry

Class

JEE Class 12

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JEE Chemistry Solved Question Paper 2014

Multiple Choice Questions

The correct increasing order of the acid strength of benzoic acid (I), 4-nitrobenzoic acid (II), 3,4-dinitrobenzoic acid (III) and 4-methoxybenzoic acid (IV) is

I < II < III < IV
II < I < IV < III
IV < I < II < III
IV < II < I < III

Choose the correct order of decreasing basic strength of the following compounds in aqueous solution

(i) C₆H₅NH₂

(ii) C₂H₅NH₂

(iii) NH₃

(iv) (CH₃)₂NH

(i) > (ii) > (iii) > (iv)
(iv) > (ii) > (iii) > (i)
(ii) > (i) > (iii) > (iv)
(iv) > (iii) > (ii) > (i)

The shortest wavelength of the line in hydrogen atomic spectrum of Lyman series when R_H = 109678 cm^-1 is

1002.7 Å
1215.67 Å
1127.30 Å
911.7 Å

4.
Arrange the following species in the correct order of their stability
C₂, Li₂, O $_{2}^{+}$ , He $_{2}^{+}$

Li₂ < He $_{2}^{+}$ < O $_{2}^{+}$ < C₂

C₂ < O $_{2}^{+}$ < Li₂ < He $_{2}^{+}$

He $_{2}^{+}$ < Li₂ < C₂ < O $_{2}^{+}$

O $_{2}^{+}$ < C₂ < Li₂ < He $_{2}^{+}$

He $_{2}^{+}$ < Li₂ < C₂ < O $_{2}^{+}$

Higher the bond order, more is the stability. The bond order of the given species can be calculated as-

MO configuration of C₂ = (6 + 6 = 12)

= σ1s², σ*1s², σ2s², σ*2s², $π 2 p_{x}^{2} \approx π 2 p_{y}^{2}$

BO = $\frac{N_{b} - N_{a}}{2} = \frac{8 - 4}{2} = \frac{4}{2} = 2$

MO configuration of Li₂ = (3 + 3 = 6)

= σ1s², σ*1s², σ2s²

BO = $\frac{4 - 2}{2}$ = 1

MO configuration of O₂ = (8 + 8 -1 = 15)

= σ1s², σ*1s², σ2s², σ*2s², σ2p $_{z}^{2}$ , $π 2 p_{x}^{2} \approx π 2 p_{y}^{2}, π * 2 p_{x}^{1}$

BO = $\frac{2 - 1}{2} = \frac{1}{2} = 0.5$

Thus, the order of bond orders of the given species is

He $_{2}^{+}$ < Li₂ < C₂ < O $_{2}^{+}$

Since, bond order α stability.

Thus, order of stability will also be the same.

Molecular formulae and shapes of some molecules are given below. Choose the incorrect match.

NH₃ - Trigonal pyramidal
SF₄ - Tetrahedral
ClF₃ - T-shaped
PCl₅ - Triginal bipyramidal

If two moles of an ideal gas at 500 K occupies a volume of 41 L, the pressure of the gas is (R = 0.082 L atm K^-1 mol^-1)

2 atm
3 atm
4 atm
5 atm

At 273 K, the density of a certain gaseous oxide at 2 atm is same as that of dioxygen at 5 atm. The molecular mass of the oxide (in g mol^-1) is

Which of the following are isoelectronic species?

(i) NH₃

(ii) CH $_{3}^{+}$

(iii) NH $_{2}^{-}$

(iv) NH $_{4}^{+}$

Choose the correct answer from the codes given below.

(i), (ii), (iii)
(ii), (iii), (iv)
(i), (ii), (iv)
(i), (iii), (iv)

The salt of an alkali metal gives violet colour in the flame test. Its aqueous solution gives a white precipitate with barium chloride in hydrochloric acid medium. The salt is