Homework Problems: Chapter 5

  1. To convert a given number of moles into the number of atoms, you would

            multiply by which of the following factors?

a. 6.02 x 1023 atoms/1 mol    b. 1 mol/6.02 x 1023 atoms    c. 1.66 x 10-24 atoms/1 mol  

d. 1 mol/1.66 x 10-24 atoms

  1. How many molecules of water are there in 4.00 mol of water?

a. 1.41 x 1024           b. 3.41 x 1023          c. 2.41 x 1024           d. 6.45 x 1024

  1. How many grams of sulfur make up 3.01 mol of sulfur atoms? [Use atomic

             weight: S, 32.06 g/mol]

a. 1.81 x 1024 g b. 32.06 g   c. 3.01 g    d. 0.150 g               e. 96.5 g

  1. Calculate the number of grams in 0.125 moles of nitrogen molecules.

a. 0.0107 g              b.  3.50 g                c. 112 g   d. 1.75 g   e. 0.0046 g

  1. How many atoms are in a 10.0 g sample of molybdenum (Mo)?

a.  1.10 x 1023  b. 1.43 x 1023 c. 6.27 x 1022 d. 2.53 x 1026 e. 5.78 x 1026

  1. The Haber process combines nitrogen gas with hydrogen gas at high temperature and pressure to produce ammonia:

         ___N2(g) + ___H2(g) --> ___NH3(g)

The coefficient of the hydrogen in the balanced equation is

             a.  1.   b.  2.    c.  3.    d.  6.

  1. What is the sum of all coefficients when the following equation is balanced?

                  C2H6(g) + O2(g) ------> CO2(g) +  H2O(g)

 a. 13       b. 15    c. 17     d. 19       e. 21

  1. Given Fe2O3(s)  + 3CO(g) à 2Fe(s) + 3CO2(g) ;  How many CO molecules are required     to react with 25 formula units of Fe2O3?
    1. 15 CO molecules b. 75 CO molecules c. 55 CO molecules  d. 40 CO molecules
  2. How many moles of HCl can be formed when 2 mol of hydrogen gas react

with chlorine? H2(g) + Cl2(g) ------> HCl(g) (unbalanced)

a. 0.5 mol b. 1 mol c. 2 mol d. 4 mol e. 8 mol

  1. Fe2O3(s)   + 3CO(g)   à 2Fe(s)   + 3CO2(g); What mass of CO is required to react with 146 grams of Fe2O3?
         a.  16.3 g CO     b. 56.8 g C   c. 76.7 g  d. 94.7 g CO     e. 14.2 g CO

11.  For the reaction given below, how many moles of AlBr3 will be produced if 12 moles of Br2  react with 8 moles of aluminum?

          2Al(s)  +  3Br2(l)  --->  2AlBr3(s)

a.       4    b. 8    c. 12   d. 16  e. 20

  1.             In the reaction given below, how many grams of sodium metal are consumed if 14.2 g of chlorine gas react to produce 23.4 g of sodium chloride?       

                     2Na(s)  +  Cl2(g)  --->  2NaCl(g)

a. 4.3 g   b. 9.2 g  c. 14.2 g  d. 18.8 g e. 33.0 g

  1.  The efficiency of a particular synthesis method is evaluated by determining the:

a.       limiting reactant  b. theoretical yield                  c.  percent yield             d.   molecular weight of the product        e.  stoichiometric coefficients

14.     If 95.0 g of cesium reacts in sufficient chlorine to produce cesium chloride, what is the theoretical yield?

2Cs(s)  +  Cl2(g)    --->  2CsCl(s) 

a.     95.0 g      b. 120. g          c. 146 g            d. 236 g           e. 285 g

  1.   If 4 Fe3O4(s) (4.00 g) + O2(g) (excess)  ®  6Fe2O3  and  actual yield  is  3.55 g, what is the theoretical yield of Fe2O3?

a. 50.5 %       b. 91.1 %       c. 85.7 %        d.  100 %