Question

How much Ca(OH)2 must be added to initially pure water to raise the pH to 11? Express your answer in mass concentration.

Answer 1

Ca(OH)2 is a strong base so it will dissociate completely

first find out the concentration of [OH-] using

pH + pOH = 14
pOH = 14 - 11 = 3

pOH = -log[OH-]

3 = -log[OH-]

[OH-] = 10^-3

[OH-] = 0.001 M

Ca(OH)₂ (aq) ---------> Ca²⁺ (aq) + 2OH^-

we know only concentration of [OH-]

but one mole of Ca(OH)2 is giving 2wo mole of [

so accordinglyOH-]

Ca(OH)₂ (aq) ---------> Ca²⁺ (aq) + 2OH^-

0.001/2                       0.001/2   +   0.001

so thye concentration of Ca(OH)2 = 0.0005 = 5 x 10^-5 M

you should give the volume then only we can say mass concentration