Question

Please show all the work for the following pH calculations.

What’s the pH if [H+] = 10 mM?

What’s the pH if [OH-] = 1 x 10-6 M?

What’s the hydrogen ion concentration if pH = 4.76?

What’s the hydrogen ion concentration if hydroxide concentration is 1 nM?

What’s the pKa of a pH 6 solution with 0.075 M and 0.025 M respectively of HA and A-?

Answer 1

[H+] = 10 mM

We know the formula of pH

pH = - log [H+]

we are given H+ concentration in mM that should be converted to M

[H+] in M = 10 mM x 1 M / 1000 mM = 0.01 M

pH = - log ( 0.01 )

pH = 2

2). [OH-]= 1E-6 M

From the concentration of OH- we can get pOH.

pOH = - log [ OH- ]

= - log ( 1.E-6)

= 6

Now we can find pH

pH = 14 – pOH

= 14 – 6 = 8

So the pH of the solution = 8.0

3 )

pH = 4.76

pH = - log [H +]

lets take antilog of both both side

antilog (-pH ) = [H+]

[H+] = antilog ( -4.76)

[H+] = 1.73 E-5 M

4).

[OH-]= 1 nM

Conversion of nM to M

[OH-] in M = 1 nM x 1 E-9 M / 1nM

[OH-]= 1 E-9 M

We know the ionic product of water

[H+] [OH-]= 1.0 E-14

[H+] = 1.0 E-14 / 1 E-9

= 1.0 E-5 M