To 1L solution containing 0.1 mol each of $N H_{3}$ and $N H_{4} C l, 0.05$ mol of NaOH is added. The change in pH will be $(p K_{b} f o r N H_{3} = 4.74)$

40 m l

0.1 M

ammonia solution is mixed with

20 m l

0.1 M H C l

. What is the pH of the mixture?

[Given:

p K_{b}

of ammonia solution is

4.74

]

Q. What volume of 0.2 M

N H_{4} C l

solution should be added to 100 ml of 0.1 M

N H_{4} O H

solution to produce a buffer solution of

p H = 8.7

?
Given :

p K_{b} o f N H_{4} O H = 4.7; antilog (0.6) = 4

Join BYJU'S Learning Program

What volume of 0.1 M HCl must be added to 500 ml, 0.25 M NH3 to have a buffer of pH = 9.74 [Given : pKb of NH3 is 4.74, log3=0.48]

The correct option is B 312.5 mLWe know that pOH=14∴pOH=14−pH=14−9.74⇒pOH=4.26 We know for a buffer solution pOH=pKb+logsaltbase⇒4.26=4.74+logsalt0.125−0.1V⇒−0.48=log0.1V0.125−0.1V⇒log3=log0.125−0.1V0.1V⇒0.3V=0.125−0.1V⇒0.4V=0.125⇒V=1.254=0.3125 L⇒V=312.5 mL

What volume of 0.1 M $H C l$ must be added to 500 ml, 0.25 M $N H_{3}$ to have a buffer of pH = 9.74
[Given : $p K_{b}$ of $N H_{3}$ is $4.74, log 3 = 0.48$ ]