100 ml solution having 0.2 M HA (weak acid, `K_(a), = 1.0x10^(-5) )` and 0.2 N NaA, 200 ml of 0.1 M NaOH has been added. Furthermore, diluted to IL. Which of the following statement is correct?

Options

A. Initially , the solution has pH equal to 5, that is before additions of NaOH
B. In the final solution , the concentration of `[OH^(-) ] is 10^(-9) ` M.
C. After the addition of NaOH , the pH of solution increase by four units.
D. After the addition of base, the solution losses buffering action and can be restored after the addition of acid.

Answer

A, D

Explanation

Initially acid buffer is present

` pH =5 + log ""(0.2)/( 0.2) = 5`
(b) after dilution to 1 lt,
` [HA] =0.02 N, [NaA ]= 0.02 N`
` [NaOH ]=0.02 N`
` {:( NaOH +, HA to , NaA + H_2O) , ( 0.02 N , 0.02N , -),( -,-,0.02N):}`
` therefore ` Due to addition of NaOH , buffer disappeared & salt is formed
` pH =7+ ( 5)/(2) +(1)/(2) log (4 xx 10 ^(-2) ) = 8.8 `