Question

What is the volume of the solution produced when enough water is added to 42.0 g of mgcl2 ⋅ 6h2o to yield a solution that has a cl- ion concentration of 0.500m?

Answer 1

827 mL

Step-by-step explanation:

To answer this question we use the definition of Molarity:

Molarity = mol / L

[Cl⁻] = mol Cl⁻ / L

Now we calculate the moles of Cl⁻ present in 42.0 g of MgCl₂⋅6H₂O:

Molar mass of MgCl₂⋅6H₂O = 24.3 + 2*35.45 + 6*18 = 203.2 g/mol

moles of Cl⁻ = 42.0 g MgCl₂⋅6H₂O ÷ 203.2 g/mol *
`(2molCl^(-))/(1molMgCl_(2).6H_(2)O)` = 0.4134 mol Cl⁻

Finally we use the definition of molarity to calculate the volume:

0.500 M = 0.4134 mol Cl⁻ / xL

xL = 0.827 L = 827 mL