Answers and some guidance for each of the 4 problems in this exercise.

Weight volume percent (w/v %) is mass of solute divided by volume of solution expressed as a percent. 25.0 g divided by 2000 mL, then multiply by 100 to convert the fraction to a percent.

1.25% w/v

The molar mass of magnesium nitrate is 148.3 g/mol. Convert grams to moles, then divide by 2L since molarity is "moles solute per liter of solution."

0.0843 M

The mass of the solution is the sum of the mass of solute (which is 75 g) and the mass of the solvent (which is 500 g). Seventy-five g solute out of 575 total, then convert the fraction to a percent by multiplying by 100.

13.0% w/w

You can simply do this problem as a conversion, knowing that 0.2 M means 0.2 mol solute per liter of solution.

(0.20 mol/L)(0.5L) =0.1 mol

0.1 mol (119 g/mol) = 11.9 g