Question

if you have a supply of 0.50M Ca(NO3)2 solution in your laboratory. How many milliliters of this solution do you have to evaporate to get 32.8g of solid Ca(NO3)2

Answer 1

how many moles of Ca(NO3)2 in 32.8g? If it is x, then since 0.50M solution has 0.5 moles per liter, you will need 2x liters of solution.
or, 2000x mL

Answer 2

Another way but not any better.
molar mass Ca(NO3)2 = 40 + (14 + 48)*2 = 164 so 0.5M = 164/2 or 82 g/L.
82 g/L x ?L = 32.8