In: Chemistry
A. What is the molarity of sodium ions in a solution prepared by mixing 202.1 ml of 0.63 M sodium phosphate with 239 ml of 1.31 M sodium sulfide. Enter to 2 decimal places.
B. A 17.3 ml sample of a 1.49 M potassium chloride solution is mixed with 58.6 ml of a 1.34 M lead(II) nitrate solution and a precipitate forms. The solid is collected, dried, and found to have a mass of 0.5 g. What is the percent yield? Enter to 2 decimal places.
A) millimoles of Na+ from sodium phosphate = 3 x 202.1 x 0.63 = 382.0
millimoles of Na+ from sodium sulfide = 2 x 239 x 1.31 = 626.2
molarity of sodium ion = 626.2 + 382.0 / (202.1 + 239)
= 2.29 M
molarity of sodium ion = 2.29 M
B)
moles of KCl = 17.3 x 1.49 / 1000
= 0.0258
moles lead(II) nitrate = 58.6 x 1.34 / 1000
= 0.0785
2 KCl + Pb (NO3)2 --------------------------> PbCl2 + 2 KNO3
2 1
0.0258 0.0785
limiting reagent is KCl
so moles precipitate formed = 0.0258 / 2
= 0.01425
mass of precipitate = 0.01425 x 278.1
= 3.96 g
percent yield = 0.5 x 100 / 3.96
percent yield = 12.62 %