Solubility math for gen chem

[MaizeGoBlue]

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Hi all,

I'm having trouble with solubility problems in gen chem. However, it's not the problem itself that is troubling me. It's the math right at the end of the problem, which I struggle doing. For example, in a specific problem, the Ksp = [Pb2+]^1 * [Cl-]^2. After plugging in numbers, you get Ksp = (0.016)^1*(0.032)^2. This is the part I have trouble with. The answer is 1.6 x 10^-5, but I don't get how to solve that. Help? Is there some easy way to do this that I'm missing?

 

[alexis2010]

Work with scientific notation
1.6*10^-2*(32*10^-3)^2= (1.6*10^-2)*32^2*10^-6. 32^2=2^10=1024
1.6*1024*10^(-8). You can round 1024 to 1000 and you get 1.6*1000*10^(-8) = 1.6*10^(-5)

 

[Lnguyen7]

(0.016)^1*(0.032)^2 = (16x10^-3)(32x10^-3)^2 = (16x10^-3)(32^2*10^-6) = 16*32^2*10^-9
Approximate 32 to 30, so 32^2 ~ 900. Since we approximate 32 to 30, the actual answer is higher than 900, you can approximate it to 1000
So 16*32^2*10^-9 = 16*1000*10^-9 = 1.6*10^4*10^-9 = 1.6*10^-5