Question

When 0.2 moles of HCl is added to 1 litre of a solution containing IM acetic acid and Imole of acetate
ions in 1 litre solution. If K for acetic acid is 1.8 x 10 . Then, pH of the resulting solution is [ ]
a) 2.36
b) 3.45
c) 4.57
d) 5.68
​

Answer 1

Answer:

−log1.8×10  

−5

=4.5687

Explanation:

On adding HCl, the free hydrogen ions will combine with CH  

3

COO  −   ions to form CH  

3  COOH . Thus the concentration of acetic acid increases while that of CH  

3COO  

−

 ions decreases

[CH  

3

​  

COOH]=(0.2+1)=1.2mol litre  

−1

 

[Salt]=(1−0.2)=0.8mollitre  

−1

 

Applying Henderson's equation

pH=log  

[Acid]

[Salt]

​  

−logK  

a

​  

 

=log  

1.2

0.8

​  

−log1.8×10  

−5

=4.5687