Dear student
91 % acid by mass means 91 g acid in 100 g solution.
Density = 1.83 g/mL
Volume of solution = mass/density
= 91/1.83
= 49.73 mL
Molar mass sulpuric acid, H2SO4 = 2 x 1 + 32 + 4 x 16 = 98 g/mol
Number of moles of sulphuric acid = mass/molar mass
= 91/98
= 0.93
Molarity = number of moles/ volume of solution in litres
= 0.93/0.0497
= 18.71 M
Applying,
M1V1= M2V2
18.71 x V = 0.5 x 3.5
V = 0.093 L
= 93 mL
Thus, 93 ml of concentrated acid is required to prepare 3.5L of 0.50 M H2SO4
Regards
Arun (askIITians forum expert)