Answer
.05M
Work Step by Step
.424 g Na2SO4 x 1 mole/106.0g x 1 mole H2SO4/1 mole Na2SO4 = .0004 moles H2SO4
Use the gram value and stoichiometry to convert to moles of sulfuric acid.
.0004 / .0800 L = .05M
Use the molarity formula (M = moles solute/L solution) to find the molarity of the sulfuric acid.