Question

Ph of 0.001M Ca (OH)2

Answer 1

Explanation:

Calculating the pH of a solution of Ca(OH)2. My attempt:As 2.8g of CaO dissolves in 1l water the molarity of the solution is 0.05M. So,the concentration of OH- ions in the solution is 0.1M.So pOH is 1 and hence pH is 13. But, the answer is given to be 12.6.

Answer 2

Answer:

The molecular weight of Ca(OH)2 is 73.093

Solubility is 1.73 g/L at 20 °C

Since 1 mole is 73.093 g

∴ 0.001 mole is 0.001*73.093 = 0.073093g

In other words solution is completely soluble.

C

a

(

O

H

)

2

<=>

C

a

+

2

+

2

O

H

−

Since a % dissociation is 80%, available Ca(OH)2 for dissociation is

0.001* 80/100 = 0.0008M, but 1 mole of Ca(OH)2 gives 2 moles of OH

∴ [OH] = 0.0016

-log[OH] = pOH = 2.796

∴ pH = 14 - 2.796 = 11.204 ≈ 11.20

pH of 0.001M solution of Ca(OH)2 is 11.20