How do you do this please help

Question

Calculate the mass of solute (in grams) needed to prepare the following solution.

925 mL of 0.25 M Sn₃(PO₃)₄ solution.

______unit:______

Answer 1

Molar mass Sn₃(PO₃)₄ = 672 g / mole

Converting 925 mls to L: 925 mls x 1 L / 1000 mls = 0.925 L

0.25 M Sn₃(PO₃)₄ = 0.25 mols Sn₃(PO₃)₄ / L solution

Since we need only 0.925 mols / L ...

0.25 mols / L x 0.925 L = 0.231 moles Sn₃(PO₃)₄ needed

0.231 mols Sn₃(PO₃)₄ x 672 g / mol = 155 g Sn₃(PO₃)₄ needed = 160 g Sn₃(PO₃)₄ needed (2 sig. figs.)