Note the chemical formula is Zn+H2SO4+7H20 > ZnSO4(H2O)7+H2 . Given we have 5 grams of zinc, we wish to find the number of moles of zinc. The molar mass is 65.409g. Thus there are 5/65.409=.076 moles of zinc. Since the ratio is 1-1 zinc/sulfuric acid we need .076 moles of sulfuric acid. That is .076/.250 liters of sulfuric acid. That is, .304 liters.