Help me understand how i calculate the percentage of mass

Question

Answer 1

To find the mass of solution, we use the density of 1.12 g/ml:

1.12 g/ml x 300 ml = 336 g

To find the molar concentration of H2SO4, we first must find the mass of H2SO4, then convert that to mols of H2SO4:

The % H2SO4 is 20%, so the mass of H2SO4 is 20% x 336g = 67.2 g H2SO4

Taking the molar mass of H2SO4 as 98.1 g /mol, we find the moles:

67.2 g x 1 mol / 98.1 g = 0.685 mols H2SO4

Finally the molarity is mols / liter = 0.685 mols / 0.300 L = 2.28 M