Question

Calculate the pH of each of the solutions and the change in pH to 0.01 pH units caused by adding 10.0 mL of 2.39-M HCl to 340. mL of each of the following solutions. Change is defined as final minus initial, so if the pH drops upon mixing the change is negative.

a) water pH before mixing =

pH after mixing=

pH change =

b) 0.182 M C2H3O21- pH before mixing =

pH after mixing=

pH change =

c) 0.182 M HC2H3O2

pH before mixing =

H after mixing=

pH change =

d) a buffer solution that is 0.182 M in each C2H3O21- and HC2H3O2

pH before mixing =

pH after mixing=

pH change =

Answer 1

a) Concentration of HCl is after mixing,

Now to calculate the pH,

b) To find the pH before mixing, the following ICE table is used.

	CH3COO-	CH3COOH	OH-
Initially	0.182M	-	-
Dissociated/Formed	-x	x	x
At equilibrium	0.182-x	x	x

Therefore, we can write,

Now to calculate the pH after addition,

Moles of CH3COO- neutralized is given by,

Calculating the new pH, similar to above,

c) pH before mixing,

The pH after addition is as follows.

d) For a buffer,

pH after addition is calculated using a ice table.

	CH3COO-	H+	CH3COOH
Initially	0.1768M	0.068M	0.1768M
Dissociated/Formed	0.1768-0.068M	0	0.1768+0.068M
At equilibrium	0.1088M	0	0.2448M