Question

What mass of Na2SO4 is needed to make 2.5L of 2.0M solution? (Na=23g; S=32g; O=16g)

Answer 1

The molar mass of Na₂SO₄ - 
2 x Na - 2 x23 = 46
1 x S - 1 x 32 = 32 
4 x O - 4 x 16 = 64 
total = 46 + 32 + 64 = 142 g/mol
the molarity of solution - 2.0 M 
in 1 L of solution , 2.0 moles
Therefore in 2.5 L - 2 mol/L x 2.5 L = 5 mol
then the mass of Na₂SO₄ required = 142 g/mol x 5 mol = 710 g

Answer 2

Answer:

710

Explanation: