HOMEWORK HELP

Question

Determine the molarity of a solution formed by dissolving 468 mg of MgI2 in enough water to yield 50.0 mL of solution.
0.0337 M
0.0651 M
0.0107 M
0.0297 M
0.0936 M

Answer 1

Find the molecular weight of MgI₂ in grams per mole, divide the given mass by the molecular weight to get the number of moles of MgI₂, and then divide the number of moles by the volume of solution to get concentration.

 

Molecular weight:

 

Mg + 2I = 24.3 + 2(126.9) = 278.1 g/mol

 

Number of moles:

 

(468 x 10^-3 g)/(278.1 g/mol) ≅ 1.683 x 10^-3 moles

 

Concentration:

 

[MgI₂] = (1.683 x 10^-3 moles)/(0.050 L) ≅ 0.0337 moles/L = 0.0337 M