Question

What weight of magnesium chloride (MgCl2, formula weight 95.3; Mg2, atomic weight = 243; Cl, atomic weight-35.5) is required to prepare 1,000 mL of a solution that contains 5.0 mEq of magnesium?

Answer 1

238.25 mg

Explanation:

Given:

Molar mass of MgCl₂ = 95.3

atomic weight of Mg₂ = 243

Atomic weight of Cl = 35.5

Volume of solution required = 5.0 mEq of magnesium

Now,

mEq =
`\frac{\textup{Weight in mg*Valency}}{\textup{Atomic mass}}`

on substituting the values, we get

5 =
`\frac{\textup{Weight in mg*2}}{\textup{95.3}}`

or

weight of magnesium chloride = 238.25 mg

Therefore,

the required mass of MgCl₂ is 238.25 mg