1) When aqueous solutions of K 2 SO 4 and Pb(NO 3 ) 2 are combined, PbSO 4 preci
ID: 1028187 • Letter: 1
Question
1) When aqueous solutions of K2SO4 and Pb(NO3)2 are combined, PbSO4 precipitates. Calculate the mass, in grams, of the PbSO4 produced when 2.44 mL of 0.175 M Pb(NO3)2 and 4.28 mL of 0.78 M K2SO4 are mixed. Calculate the mass to 3 significant figures.
2)The following pairs of soluble solutions can be mixed. In some cases, this leads to the formation of an insoluble precipitate. Decide, in each case, whether or not an insoluble precipitate is formed.
NaCl and K3PO4
Li2SO4 and CaCl2
Ba(NO3)2 and Ag2SO4
Na2CO3 and MnCl2
Li2S and MnBr2
3)How many moles of Ag+ ions are present in 51.1 mL of a 0.641 M Ag2SO4 solution?
Explanation / Answer
Ans 1
Balanced reaction
Pb(NO3)2 (aq) + K2SO4(aq) PbSO4(s) + 2KNO3(aq)
Moles of Pb(NO3)2 = molarity x volume
= 0.175 mol/L x 0.00244 L
= 0.000427 mol
Moles of K2SO4 = molarity x volume
= 0.78 mol/L x 0.00428 L
= 0.0033384 mol
Moles of Pb(NO3)2 < Moles of K2SO4
Limiting reactant = Pb(NO3)2
From the stoichiometry of the reaction
Moles of PbSO4 formed = Moles of Pb(NO3)2 consumed
= 0.000427 mol
Mass of PbSO4 formed = moles x molecular weight
= 0.000427 mol x 303.2626 g/mol
= 0.129 g
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