Reactions Practice Test - Answer Key

 

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  1. A 1.42 g sample of pure compound with formula M2SO4 was dissolved in water and treated with an excess of aqueous calcium chloride, resulting in the precipitation of all the sulfate ions as calcium sulfate.  The precipitate was collected, dried, and found to weigh 1.36 g.  Determine the identity of M.

    M = Sodium

     

     

  2. What mass of Na2CrO4 is required to precipitate all of the silver ions from 75.0 mL of a .0100 M solution of AgNO3?

    0.0607 g Na2CrO4

     

     

  3. If 250 mL of 0.350 M Ba(OH)2 is reacted with 300 mL of 0.290 M H3­PO4.  What is the concentration of [H+] and [–OH]?

    [–OH] = 0
    [H+] = 0.156 M

     

     

  4. A student added 50.0 mL of an NaOH solution to 100.0 mL of 0.400 M HCl.  The solution was then treated with an excess of aqueous chromium (III) nitrate, resulting in formation of 2.06 g of precipitate.  Determine the concentration of the NaOH solution.

    2.00 M NaOH

     

     

  5. Hydrochloric acid (75.0 mL of 0.250 M) is added to 225.0 mL of 0.0550 M Ba(OH)2 solution.  What is the concentration of the excess H+ or –OH left in the solution?

    0.0200 M –OH

    6.  

     

  6. What is the theoretical yield, in grams, of  solid aluminum hydroxide that would be produced when 50.0 mL of 0.200 M aluminum nitrate is added to 200.0 mL  of 0.100 M KOH?

    0.520 g aluminum hydroxide

     

     

  7. When aqueous solutions of Na3PO4 and Pb(NO3)2 are mixed Pb3(PO4)2 precipitates.  What volume of 0.40M Na3PO4 is required to precipitate all the lead from 800mL of 1.2 M Pb(NO3)2?

    1.6 L Na3PO4

     

     

  8. If 4.00-g of phosphoric acid is neutralized with 100 mL of an NaOH solution, what is the molarity of the NaOH solution?

    1.22 M NaOH

     

     

  9. A solution of potassium permanganate is standardized by titration of a
    295 mg sample of primary standard sodium oxalate (Na2C2O4, MW = 134 g/mol) and requires 32.15 mL KMnO4 to reach the equivalence point.  Balance the reaction and calculate the molarity of the KMnO4 solution.

    MnO4-  +  C2O42-      →  Mn2+  +  CO2

    16 H+ + 2 MnO4- + 5 C2O42-    à 2 Mn2+ + 8H2O + 10 CO2
    0.0274 M KMnO4

    10.  

     

  10. Identify the substance that is reduced in a lead-acid battery if the following equation describes the reaction that takes place as the battery is discharged.

    Pb (s)  +  PbO2 (s)  +  2H2SO4 (aq)  →  2PbSO4 (s) +  2H2O (l)

    PbO2

    11.  

     

  11. Assign the oxidation state of nitrogen in each of the following compounds.
    • N2H4                           (-2)
    • NO3                            (+6)   
    • (NH4)2HPO4              (-3)

       

       

  12. Identify the oxidizing agent in the reaction:

    Zn (s) + 2 HCl (g) → ZnCl2 (aq) + H2 (g)

    HCl

    13.  

     

  13. Identify the reducing agent in the reaction:

    Pb (s) + PbO2 (s) + 2 H2SO4(aq) → PbSO4 (s) + 2 H2O (l)

    Pb

    14.  

     

  14. Which of the following pairs of aqueous solutions will react when mixed?
    • MgCl2 (aq) + 2KOH (aq) à Mg(OH)2 (s) + 2KCl(aq)                            precipitation
    • HCl(aq)  + LiOH(aq)  à H2O(l)  + LiCl(aq)                              acid/base

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