﻿ Vapour density of a volatile substance is 4 (CH4 = 1). Its molecular weight would be: from Chemistry NEET Year 2003 Free Solved Previous Year Papers

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# 1.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

= $\frac{16}{2}$ = 8

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

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

2.

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.

3.

If Kb of HCN is 4.0 $×$ 10-10, then the pH of 2.5 $×$ 10-1 molar aqueous HCN is

• 2.0

• 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

4.

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.

5.

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

0.2 N is the strength of the resulting acid mixture.

6.

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.

7.

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.

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.

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.

10.

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.