CHEM 35

General Chemistry

Quiz #5

 

October 27, 2000

Name:      Shuns, Sol Lew                     

 

1.               A sample of 70.5 mg of K3PO4 (MW = 212.266 g/mol) is added to 15.0 mL of 0.050 M AgNO3, resulting in the formation of a precipitate.

 

a.     (2 pts) Write a balanced net ionic equation for this reaction.

 

     3 Ag+(aq) + K3PO4(s) ® Ag3PO4(s) + 3 K+(aq)

 

b.      (2 pts) What is the limiting reactant in this reaction.

 

0.0705 g K3PO4 x    mol K3PO4       x 3 mol AgNO3  x      L       x 1000 mL =

                 212.266 g K3PO4     1 mol K3PO4   0.050 mol AgNO3    L

 

                        19.9 mL AgNO3

                              (needed)

            Only 15 mL AgNO3 available, so

                AgNO3 is LIMITING REACTANT

 

 

c.      (2 pts) Calculate the mass (g) of precipitate formed in this reaction

 

0.0150 L AgNO3 x  0.050 mol AgNO3 x 1 mol Ag3PO4  x 418.576 g Ag3PO4 =

                        L          3 mol AgNO3          mol Ag3PO4

 

            = 0.10464 g Ag3PO4

          = 0.10 g Ag3PO4

 

2.     (2 pts each) Each of the following reactions produces a gas as one of its products. For each reaction, write a balanced reaction equation.

a.     CaCO3(s) + HNO3(aq) ®  products

 

     CaCO3(s) + 2 HNO3(aq) ® Ca(NO3)2(aq) + H2O(l) + CO2(g)

 

 

b.     Cu(s) + HNO3(aq) ® products

 

     Cu(s) + 2 HNO3(aq) ® Cu(NO3)2(aq) + H2(g)