how many grams of solid magnesium chloride MgCl2, need to be used to make 250mL of .50 m solution?

Question

(MgCl2 molar mass = 95.21 g/mol)

Answer 1

OK...you're using m (and not M), so I'm going to assume it's correct and you want a 0.50 molal solution, i.e. 0.50 mol in 1000g of solution.

Since 1 mole of MgCl2 has a mass of 95.21g,
0.5 mole has a mass of 95.21*0.5 = 47.605g

These are present in 1000g of solution. The problem requires 250mL. Assuming that the density of the solution is approximately equal to the density of water, which is 1 g/mL, then the weight of the solution is 250g

So: 47.605g in 1000g
? in 250g

47.605*250/1000 = 11.90 g [Weight required]

Answer 2

Given:
MgCL2 molar mass= 95.21
Total volume = 250 ml
Required M = 0.50
Needed = weight of MgCL2

Make use of the formula"

Weight in grams of Mg Cl2 = required M (Molar solution) X desired volume (in Liters) X MW (molar mass)

Simplifying the formula :

W = 0.50 X .250 X 95.21

W = 11.90125 grams - answer

Answer 3

the moles of MgCl2 in the solution : 0.5 * 0.25 = 0.125 mols
the grams of MgCl2 : 0.125 * 95.21 = 11.9g