Question

What is the total concentration of ions in the solution obtained by dissolving 7.44 g of Na2SO4 in 200.0 mL of water? (Molar mass of Na2SO4 = 142.04 g/mol)

Answer 1

Molarity of Na2SO4 solution = moles of Na2SO4 x 1000 / volume of solution

Given, mass of Na2SO4 = 7.44g, volume of solvent = 200.0 mL,

then moles of Na2SO4 = 7.44 / 142.04

= 0.0524

now, molarity of Na2SO4 solution = 0.0524 x 1000 / 200.0

molarity of Na2SO4 solution = 0.262M

Na2SO4 ionizes as: Na2SO4 <====> 2Na+     +      SO42-

So, concentration of Na+ = 2 x 0.262 = 0.524M

concentration of SO42- = 0.262

Total concentration of ions = 0.524M + 0.262

= 0.786M