﻿ If Kb of HCN is 4.0 × 10-10, then the pH of 2.5 × 10-1molar aqueous HCN is from Chemistry NEET Year 2003 Free Solved Previous Year Papers

## Test Series

Take Zigya Full and Sectional Test Series. Time it out for real assessment and get your results instantly.

## Test Yourself

Practice and master your preparation for a specific topic or chapter. Check you scores at the end of the test.

# NEET Chemistry Solved Question Paper 2003

#### Multiple Choice Questions

1.

One gram of mass is equal to :

• 9 x 1020 ergs

• 7 x 1015 ergs

• 5 x 1010 ergs

• 3 x 105 ergs

A.

9 x 1020 ergs

According to E = mc2

m = 1gm

c= 3$×$1010 cm sec-1

$\therefore$E = 1gm$×$(3$×$1010 cm sec-1)2

= 9$×$ 1020 ergs

1 gm of mass is equal to 9 x 1020 ergs. Ergs or ergon (a Greek word) is the amount of work done by a force of one dyne exerted for a distance of one centimeter.

2.

75 c.c. of N/5 H2SO4, 10 c.c. of N/2 HCl and 30 c.c. of N/10 HNO3 are mixed together. The strength of the resulting acid mixture is:

• 0.1N

• 0.2N

• 0.3N

• 0.4N

B.

0.2N

Normality of the resulting mixture

$=\frac{{\mathrm{N}}_{1}{\mathrm{V}}_{1}+{\mathrm{N}}_{2}{\mathrm{V}}_{2} +{\mathrm{N}}_{3}{\mathrm{V}}_{3}}{{\mathrm{V}}_{1}+{\mathrm{V}}_{2}+{\mathrm{V}}_{3}}\phantom{\rule{0ex}{0ex}}=\frac{75×\frac{1}{5}+10×\frac{1}{2}+30×\frac{1}{10}}{75+10+30}\phantom{\rule{0ex}{0ex}}=\frac{15 +5+3}{115}\phantom{\rule{0ex}{0ex}}=\frac{23}{115}=\frac{\mathrm{N}}{5}=0.2\mathrm{N}$

0.2 N is the strength of the resulting acid mixture.

3.

Which of the following ions is paramagnetic?

• Cu++

• Zn++

• Ni++

• Both 'a' and 'c'

D.

Both 'a' and 'c'

Paramagnetic compounds have unpaired electrons. These are attracted to magnetic fields.

Among all the given options, Cu++ and Ni++are paramagnetic.

# 4.If Kb of HCN is 4.0 $×$ 10-10, then the pH of 2.5 $×$ 10-1molar aqueous HCN is2.0 4.7 5.0 2 x 10-5

C.

5.0

[H+]in a solution of weak acid of conc. C and dissociation constant Kc is given as

$\left[{\mathrm{H}}^{+}\right]=\sqrt{{\mathrm{K}}_{\mathrm{a}}×\mathrm{C}}=\sqrt{4.0×{10}^{-10}×2.5×{10}^{-1}}\phantom{\rule{0ex}{0ex}}=\sqrt{1×{10}^{-10}}\phantom{\rule{0ex}{0ex}}=1×{10}^{-5}\mathrm{M}\phantom{\rule{0ex}{0ex}}\mathrm{pH}=-\mathrm{log}\left[{\mathrm{H}}^{+}\right]\phantom{\rule{0ex}{0ex}}=-\mathrm{log}{10}^{-5}=5$

5.

Among the following compounds which is planar in shape is

• acetylene

• benzene

• isobutene

• methane

B.

benzene

All the carbon atoms in benzene are in sp2 state of hybridization, hence, all the six carbons and six hydrogen atoms attached with these carbon lie in a plane.

6.

Vapour density of a volatile substance is 4 (CH4= 1). Its molecular weight would be:

• 2

• 8

• 64

• 128

C.

64

Actual vapour density of methane

=$\frac{\mathrm{molecular}\mathrm{weight}}{2}$=$\frac{16}{2}$= 8

$\therefore$Vapour density of volatile substance = 8$×$4 = 32

Molecular weight of the substance = 32$×$2 = 64

7.

Which will have maximum ionization energy?

• Na

• Mg

• K

• Bi

B.

Mg

Among all the options given, Magnesium has the highest ionization energy. It is because magnesium has one more proton in its nucleus to hold on to the electrons in the 3s orbital.

8.

In an isochoric process, the increase in internal energy is equal to:

• the sum of heat absorbed and work done

• the work done

• heat absorbed

• heat evolved

C.

heat absorbed

In an isochoric process, $∆$V = 0, hence, work done P$∆$V = W = 0. So, $∆$E = q + 0. Hence, the increase in internal energy will be equal to heat absorbed by the system.

9.

The pH of blood is :

• greater than 10

• less than 6

• greater than 7 and less than 8

• greater than 8 and less than 9

C.

greater than 7 and less than 8

Human blood pH is 7.4. Therefore, option c is correct.

10.

Heat of a reaction at constant pressure is equal to:

• HP - HR

• HP + HR

• HP $×$ HR

• $\frac{{\mathrm{H}}_{\mathrm{P}}}{{\mathrm{H}}_{\mathrm{R}}}$

A.

HP - HR

Heat of a reaction at constant pressure is equal to HP - HR.