## What are the types of spectrum from the sources : (a) sun, (b) electric bulb, (c) neo

Que. What are the types of spectrum from the sources :

(a) sun, (b) electric bulb, (c) neon lamp (d) sodium salt Bunsen flame?

Ans. (a) sun― dark line absorption spectrum.
(b) electric bulb― continuos emission spectrum
(c) neon lamp―band emission spectrum
(d) sodium salt on Bunsen flame― line emission spectrum.
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14th March 2019

123

## The dissociation constant of a substituted benzoic acid at 25oC is 1.0 × 10-4. The pH of a 0.01 M solution of its sodium salt is

The dissociation constant of a substituted benzoic acid at 25oC is 1.0 × 10-4. The pH of a 0.01 M solution of its sodium salt is

Solution:

`Ka (C6H5COOH) = 1 × 10-4pH of 0.01 M C6H5COONaC6H5COO- + H2O -------> C6H5COOH + OH-1   0.01(1-h)                                 0.01 h            0.01 hKh = Kw/Ka =(0.01 h2)/(1-h) 10-14/10-4 = 10-2 h2/(1-h) (1 – h ≈ 1)[OH-] = 0.01 h = 0.01 × 10-4 = 10-6[H+] = 10-8pH = 8`

25th February 2019

71