1.) While carrying out Part A, some of the solid calcium hydroxide is inadverten

Question

1.) While carrying out Part A, some of the solid calcium hydroxide is inadvertently transferred to the beaker and titrated.

a.) Will more, less, or the same amount of HCl be used for the titration? Explain.

b. How will the mistake effect the reported molar solubility? Explain.

c. How will the mistake effect the reported Ksp? Explain

2. A sample of 3.11 mL of standardized HCl ( [0.0025] ) solution titrated 25.0 mL of a saturated Mg(OH)2

solution to the methyl orange endpoint. Calculate theKsp of Mg(OH)2.

Explanation / Answer

a) It will increase the amount of HCl because you have to also neutralize the additional OH- ions from the hitchhiking NaOH plus whatever else you are neutralizing.

b). Ksp will increase as some amont of solid will dissolve and the concentration of ions will increase.
c) molar solubility will remain constant as its fixed.

2.

First write out the balanced reaction:

Mg(OH)2 +2HCl --> MgCl2 + 2H2O

Calculate the molarity of Mg(OH)2:

3.11 mL(0.001L/1mL)(0.0025mol/L HCl) (1mol Mg(OH)2/2mol HCl)/0.025L = 0.1555 * 10-3 M Mg(OH)2

Mole ratio between Mg(OH)2 and Mg2+ is one to one and OH- is two to one

Concentration of Mg2+ ions = 0.1555 * 10-3 M
Concentartion of OH- ions = 0.311 * 10-3 M

Ksp = [Mg 2+][OH-]2
Ksp = (0.1555)(0.311)2 * 10-9
Ksp = 1.504 x 10-11

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