Question

5.0 grams of solid Ce2(SO4)3 was added to 100 mL of water.

What is the total mass?

Answer 1

If the density of the water is 1.00 g/mL, the mass of the water is 100 g and the total mass is 105 grams. If your prof is picky about the number of significant figures you need to be careful how to report that. 100 has only 1 significant figure and would be written as 1.E2 to be added to 0.050E2 to make the total. But be careful before you write 1.05E2.