The mass of solute : 16.4
Molarity is a way to express the concentration of the solution
Molarity shows the number of moles of solute in every 1 liter of solute or mmol in each ml of solution
[tex]\large{\boxed {\bold {M ~ = ~ \frac {n} {V}}}[/tex]
Where
M = Molarity
n = number of moles of solute
V = Volume of solution
mol Na₃PO₄
[tex]\tt mol=M\times V=0.2\times 0.5=0.1[/tex]
mass Na₃PO₄
[tex]\tt mass=mol\times MW\\\\mass=0.1\times 164=16.4[/tex]