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Question:

pH of saturated solution of Ca(OH)₂ is 9. The solubility product (Ksp) of Ca(OH)₂ is:

0.25×10⁻¹⁰

0.5×10¹⁰

0.125×10⁻¹⁵

0.5×10⁻¹⁵

Solution:

Correct option is A.
0.5×10⁻¹⁵
Ca(OH)₂⇌Ca²⁺+2OH⁻
pH=9
Hence, pOH=14-9=5
[OH⁻]=10⁻⁵M
Hence [Ca²⁺]=10⁻⁵/2
Thus Ksp=[Ca²⁺][OH⁻]²=(10⁻⁵/2)(10⁻⁵)²=0.5×10⁻¹⁵