Molarity is defined as the moles of solute per liter of solution. [tex]M=\frac{n}{V}[/tex]. Where M is molarity, n is the number of moles and V is the volume. First we must find the molar mass of [tex]Li_2SO_4[/tex] which is 109.98 g/mol
[tex]Li_2SO_4= 2 \times Li_{Ar} + S_{Ar} + 4 \times O_{Ar}\\= (2 \times 6.941 + 32.1 + 4 \times 16.0) = 109.98 g/mol[/tex]
[tex]820\ g\ Li_2SO_4 \times \frac{mol}{109.98\ g}= 7.46\ mol\ Li_2SO4[/tex]
Then we find the molarity using above equation
[tex]M= \frac{n}{V} = \frac{7.46 mol}{2500ml} \times\frac{1000ml}{L} = 2.98\ M[/tex]
