Question

what is the concentration of sodium ions in a 250ml solution that contains 20g of Na2SO4

Answer 1

Molar mass of Na2SO4 = 2*MM(Na) + 1*MM(S) + 4*MM(O)

= 2*22.99 + 1*32.07 + 4*16.0

= 142.05 g/mol

mass of Na2SO4 = 20 g

we have below equation to be used:

number of mol of Na2SO4,

n = mass of Na2SO4/molar mass of Na2SO4

=(20.0 g)/(142.05 g/mol)

= 0.1408 mol

volume , V = 250 mL

= 0.25 L

we have below equation to be used:

Molarity,

M = number of mol / volume in L

= 0.1408/0.25

= 0.5632 M

This is concentration of Na2SO4

So,

[Na2SO4] = 0.5632 M

[Na+] = 2*[Na2SO4] = 2*0.5632 M = 1.13 M

Answer: 1.13 M