Question

The concentration of sulfate in a sample of wastewater is to be determined by using gravimetric analysis. To a 100.0-mL sample of the wastewater is added an excess of calcium nitrate, forming the insoluble calcium sulfate (136.1 g/mol) according to the balanced equation given below. The solid calcium sulfate is dried, and its mass is measured to be 0.7272 g. What was the concentration of sulfate ion in the original wastewater sample? SO4 2– (aq) + Ca(NO3)2(aq) –––––> CaSO4(s) + 2 NO3 – (aq) A) 0.05343 M B) 0.9897 M C) 18.72 M D) 1.872 M E) 9.897 M

Answer 1

as you can see you have to calculate the mol of calcium sulfate, 1 mol of SO4 2- + 1 mol of Ca(NO3)2 and it gives 1 mol of CaSO4 so the reaction is 1:1 and you have the same amount of Ca(NO3)2 and SO4 so you just have to calculate the concentration.