# Chemistry

A sample of solid Ca(OH)2 is stirred in water at 30°C until the solution contains as much dissolved Ca(OH)2 as it can hold. A 100.-mL sample of this solution is withdrawn and titrated with 5.00 X 10^-2 M HBr. It requires 48.8 mL of the acid solution for neutralization. What is the molarity of the Ca(OH)2 solution?

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1. 1. Write the balanced equation for the titration.
2. Calculate moles HBr used in the titration. moles = M x L.
3. Using the coefficients in the balanced equation from step 1, convert moles HBr to moles Ca(OH)2.
4. You want molarity Ca(OH)2. By definition, M = moles/L; therefore, use moles from step 3 and divide by 0.1 L.

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2. Balanced equation:
2HBr + Ca(OH)2 → CaBr2 + 2H2O
1mol HBr reacts with 2mol Ca(OH)2
Use equation:
M1V1 = M2V2 *2
0.05 * 48.8 = M2*100*2
M2 = 0.05*48.8/(100*2)
M2 = 0.0122M Ca(OH)2 solution. answer to first question.

Molar mass Ca(OH)2 = 74.0932 g/mol
0.0122M solution contains: 74.0932*0.0122 *100/1000 = 0.09g/100ml

Solubility of Ca(OH)2 at 30°C = 0.09g / 100ml solution.

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