Answer:
The precipitate that will be formed is PbS
Step-by-step explanation:
Step 1: Data given
Volume of a 1.2 * 10^-3 M Pb(NO3)2 = 50.0 mL = 0.05 L
Volume of a 2.0 * 10^-4 M Na2S = 50.0 mL = 0.05 L
Step 2: Pb(NO3)2 + Na2S → 2NaNO3 + PbS
NaNO3 will dissociate in 2Na+ and 2NO3-
PbS might precipitate
Step 3: Calculate moles Pb^2+
Moles = volume * molarity
Moles Pb^2+ = 0.050 * 1.2 * 10^-3 = 6 * 10^-5 moles
Step 4: Calculate moles S^2-
Moles S2- = 0.050 L * 2.0 * 10^-4 = 1 * 10^-5
Step 5: Calculate total volume
Total volume = 50 mL + 50 mL = 100 mL = 0.100 L
Step 6: Calculate molarity
Molarity = number of moles / volume
[Pb2+] = 6*10^-5 moles / 0.100 L =6 * 10^-4 M
[S2-] = 1 * 10^-5 moles / 0.100L = 1 * 10^-4 M
Qsp = [Pb2+] [S2-]
Qsp = ( 6*10^-4 ) ( 1 * 10^-4 ) = 6*10^-8
Ksp of PbS = 3* 10^-28
Qsp >>>> Ksp this means a precipitate (PbS) will be formed