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Sir kindly give me the solution for question number 40 and 41. Please answer the question in an elaborated process

Sir kindly give me the solution for question number 40 and 41. Please answer the question in an elaborated process

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Grade:11

1 Answers

Arun
25750 Points
5 years ago
Mg(OH)2 --> Mg+2 + 2OH- 

Mg+2 = x 
2OH- = 2x 

Find a Ksp expression: 

Ksp = [Mg+2][OH-]^2 
1.2x10^-11 = [Mg+2][OH-]^2 

Now plug in x for each of the concentrations in the Ksp equation, giving: 

1.2x10^-11 = [x][2x]^2 simplify this equation 
1.2x10^-11 = 4x^3 and solve for x, 

x = 0.000144 

because for every one Mg ion that is soluble, 2 OH ions are soluble, to solve for the concentration of OH (which is required to find the pH), you must multiply x by 2 

[OH] = 2x, [OH] = 2(0.000144) = 0.000288 
pOH = -log[OH] 
pOH = -log(0.000288) = 3.54 
pH = 14.00 - 3.54 
pH = 10.4

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