Question

What is the concentration in mol L-l of a 12% solution of tetrahydrate magnesium chloride (MgCl2)?
Mg = 24.31 g mol-1
Cl = 35.45 g mol-1
H = 1.01 g mol-1
O = 16.00 g mol-1

Answer 1

The concentration in mol L-l (M) = 0.717

Further explanation

Given

12% solution of tetrahydrate magnesium chloride (MgCl₂)

Required

The concentration

Solution

Tetrahydrate magnesium chloride (MgCl₂)⇒MgCl₂.4H₂O

MW = Ar Mg+2. Ar Cl+8. Ar H + 4. Ar O

MW=24.31 + 2 x 35.45 + 8 x 1.01 + 4 x 16

MW=24.31+70.9+8.08+64

MW=167.29 g/mol

12% solution = 12 % m/v = 12 g in 100 ml solution

For 1 L solution :

$\tt \dfrac{1}{0.1}\times 12~g=120~g$

The concentration in g/L = 120 g/L

Convert grams to moles :

$\tt mol=\dfrac{120}{167.29}=0.717$