NCERT Class XI Chemistry Equilibrium Solutions

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Question : 58
Total: 73
The solubility of Sr(OH)2 at 298 K is 19.23 g/L of solution. Calculate the concentrations of strontium and hydroxyl ions and the pH of the solution.
Solution:  
Molar mass of Sr(OH)2 = 87.6 + 34 = 121.6 gmol1
Solubility of Sr(OH)2 in moles L1 =
19.23gL1
121.6gmol1
= 0.1581 M
Assuming complete dissociation, Sr(OH)2Sr2++2OH
[Sr2+] = 0.1581 M, [OH] = 2 × 0.1581 = 0.3162 M
pOH = –log (0.3162) = 0.5,
∴ pH = 14 – 0.5 = 13.5
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