Chemistry 111

Exam 2 A

 

                                                                                                Name:__________________

 

You must show your work to get credit!!  NA = 6.022 x 1023/mole.

 

1.  (A)  Adipic acid has the formula C6H10O4.  Calculate the molar mass of adipic acid.

 

 

 

 

 

(B)  How many atoms of oxygen are in 0.75 moles of adipic acid?

 

 

 

 

 

(C)  How many grams of ammonium sulfate are in 5.0 moles of the compound?

                       

 

 

 

 

2.  What volume of 5.0 M HCl(aq) is needed to prepare 750. mL of 1.25 M HCl(aq)?

 

 

 

 

 

 

 

 

 

 

3.  The first step in the Ostwald process for producing nitric acid, HNO3, from ammonia is:   4NH3(g) + 5O2(g) ® 4NO(g) + 6H2O(g).  What mass of oxygen is required to react with 45.0 grams of NH3?

 

 

 

4.   Tooth enamel is mostly hydoxyapatite which is  41.41 % by mass oxygen, 18.50  % by mass phosphorus and 0.20 % by mass hydrogen and 39.89% by mass calcium.  What is the empirical formula of hydoxyapatite?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

5.   What is the limiting reagent in the reaction of 200. g of aluminum with 700. g of Fe3O4 in the reaction:

            ____Al (s)  +  ____Fe3O4 (s)  ®  _____ Fe (s)  +  _____ Al2O3 (s)

 

 

 

 

 

 

 

 

 

 

 

 

 

6.  Balance the equations:

 

(A)  ____PH3   +  ____ O2   ®  ____ P4O10  +  ____H2O

 

 

 

 

(B)  Aqueous barium hydroxide reacts with aqueous sodium sulfate to produce solid barium sulfate and aqueous sodium hydroxide.

 

 

 

7.  Hemoglobin, which carries oxygen in the blood, has a molar mass of 64500 g/mole.  If Hemoglobin is 0.346% by mass iron, how many iron atoms are there in one molecule of hemoglobin?

 

 

 

 

 

 

 

 

 

 

8.  (A)  Complete and balance the following equations.

(B)  Write the net ionic equation for any reaction that occurs.

(C)  Label each reaction as precipitation or acid/base. 

 

(A)     Cu(NO3)2(aq)  +  NaOH(aq)  ®

 

 

 

 

 

(B)     CaCl2(aq)  +  Na2S(aq) ®

 

 

 

 

 

(C)     H3PO4(aq)  +  NaOH(aq)  ®

 

 

 

 

 

9.  What volume of 0.25 M NaOH(aq) is needed to completely neutralize 50.0 mL of 0.20M H2SO4(aq)?

 

 

 

 

 

10.  Assign oxidation numbers to each element in following:

 

(A)     N2O4                    N _________              O ____________

 

 

 

(B)     H4SiO4                 H _______      Si _________  O _________

 

 

 

(C)     AsF6–                   As _________ F _________  

 

 

 

11.  A water sample was thought to contain Hg22+or Ba2+ or Cu2+.  No reaction occurred when chloride was added to the sample.  Sulfate was then added, but no precipitate occurred.  A white precipitate occurred when carbonate was added.  What cation was in the sample?

 

 

 

12.  Balance in acid:  Br−    +   MnO4−     →   Br2   +  Mn2+