00:01
According to the question moles of weak acid h a is equal to 0 .78 and moles of n a a is equal to 0 .609 mole k a is equal to 5 .66 into 10 to the per minus 7 bk a value is equal to minus log a and this is equal to minus log 5 .66 into 10 to the 1 minus 7 and this is equal to 6 .247.
00:42
So here ha plus water gives a minus plus h3 o plus ion and using ph is equal to pka plus pka plus log a minus concentration divided by h a concentration so this is equal to the ph value would be 6 .247 plus log 0 .609 divided by 0 .708 and this is equal to the ph value will be 6 .247 plus log 0 .86 this is equal to 6 .247 minus 0 .06 5.
01:32
This is equal to the ph value will be 6 .18.
01:39
This is the answer.
01:41
And part b is adding 0 .15 mole hcl to wafer.
01:55
The volume here is volume constant and hcl react to it n .a and decreases naa.
02:04
So here a minus plus h plus gives ha.
02:11
And h .a increases the mole of h .a.
02:14
The new ph will be p .k .a.
02:19
Plus log a minus concentration divided by h .a.
02:24
Concentration.
02:25
So, and this is equal to the ph value will be 6 .247 plus log 0 .609 minus 0 .15 divided by 0 .70 0 .08 plus 0 .15.
02:45
This is equal to 6 .247 plus log 0 .459 divided by 0 .858...