﻿ A buffer solution contains 500 mL of 0.2 M CH3COONa and 500

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# 11.A buffer solution contains 500 mL of 0.2 M CH3COONa and 500 ml of 0.1 M CH3COOH .1 L of water is added to this buffer , pH before and after dilution will be (pka of CH3COOH = 4.74)3.74 5.04 5.90 7.70

B.

5.04

CH3COONa $⇌$ CH3COO- + Na+

pH of buffer = pKa + log $\frac{\left[{\mathrm{CH}}_{3}{\mathrm{COO}}^{-}\right]}{\left[{\mathrm{CH}}_{3}\mathrm{COOH}\right]}$

= 4·74 + log

= 5.04

pH of a buffer does not change with dilution .

12.

What is binding energy in ${}_{5}{}^{11}\mathrm{B}$ nucleus , if mass is 0.08181 amu ?

• 1.2 x 10-4 erg/nucleus

• 8.2 x 10-4 erg/nucleus

• 10.2 x 10-4 erg/nucleus

• 1.9 x 10-4 erg/nucleus

13.

Among third row elements , the IP value :

• irregularly changes from left to right across the third row

• increases from left to right across the third row

• decrease for Na to Ar

• remains constant

14.

Hydrofluoric acid shows hydrogen bonding due to :

• high electron affinity of fluorine

• high bond dissociation energy of fluorine

• high electronegativity of fluorine

• none of the above

15.

The conjugate base of (CH3)2NH2+ is :

• (CH3)3N

• (CH3)2NH

• (CH3)2N-

• (CH3)2N+

16.

Metals are good conductor of electricity because they contain :

• a network structure

• ionic bonds

• very few valence electrons

• free electrons

17.

Which is the strongest acid ?

• ClCH2COOH

• CH3COOH

• Cl2CHCOOH

• CCl3COOH

18.

Which of the compound is optically active ?

• 1 - butanol

• Ethanol

• 2 - butanol

• Isopropyl alcohol

19.

Crystalline form of silica is called :

• crystalline silicon

• quartz

• rock

• talc

20.

The elements commonly used for making transistors are :

• Ga and In

• C and Si

• P and As

• Si and Ge