2. A solution is prepared by dissolving 1.50 g of Pb(NO3)2 in a small amount of water and diluting to a total volume of 250.00 mL.
a. Write a chemical equation (with phase symbols) to show what happens to a formula unit of Pb(NO3)2 when it is dissolved in water.
b. What is the molarity of this solution?
c. If a 25.00 mL sample of this solution were removed and diluted to a total volume of 100.00 mL, what would be the molarity of the diluted solution?
a) Pb(NO3)2(s) ----> Pb2+(aq) + 2NO3-(aq)
b) n = m/Mr = 1.50/331 = 0.0045 mol 0.0045 mol in 250 ml x mol in 1000 ml x = 0.018 mol/1000 ml = 0.018 M
c) in 1000 ml is 0.018 mol in 25 ml is x x = 0.00045 mol 0.00045 mol in 100 ml x mol in 1000 ml x = 0.0045 M