Description
Explanation & Answer
1) 1.50 mols / 0.50L = 3.0 M (with sigfigs in mind)
2) First convert grams to mols. The molar mass of KI is 165.998 g/mol. Converting...
58.5 g * (1 mol) / (165.998 g) = 0.352413 mols
the molarity is given by....
0.352413 mols / 10.L = 0.35 M (with sigfigs in mind)
3) First convert 5 micro grams Pb to grams Pb....
5ug = 5 x10^-6 g
To find ppb divide mass of Pb by mass of solution and multiply by 10^9...
(5x10^-6) / (200g) * 10^9 = 25 (if sigfigs are important, our answer should have only one sigfig. So our answer should be 30 ppb or IF YOU USE THE FIVE-EVEN RULE: 20 ppb )
4) given ppm, we work backwards to find the ratio of arsenic in the sample. First divide by 10^6...
5 / 10^6 = 5x10^-6
We know the amount of arsenic, which we'll denote A, in 50.0 g of sample has the ratio 5x10^-6. So we can write...
5x10^-6 = A / 50.0g
solving for A....
A = (5x10^-6) (50.0g) = 2.5 x10-4 g or 0.25 mg (again, if sigfigs are important: 0.30 mg or with the five-even rule in effect: 0.20 mg)
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