Hydrogen sulfide was passed through a 20% solution of lead nitrate weighing 250 g. Calculate the mass of the lead sulfide formed.

given:
w (Pb (NO3) 2) = 20%
m solution (Pb (NO3) 2) = 250 g
to find:
m (PbS)
decision:
Pb (NO3) 2 + H2S = 2HNO3 + PbS (sediment)
m substance (Pb (NO3) 2) = m solution * w = 250 g * 0.2 = 50 g
n (Pb (NO3) 2) = m: M = 50 g: 331 g / mol = 0.15 mol
n (Pb (NO3) 2): n (PbS) = 1: 1 = 0.15 mol
m (PbS) = n * M = 0.15 mol * 239 g / mol = 35.85 g
Answer: 35.85 g