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LESSSON 24 SOLUTION STOICHIOMETRY

eg. 250 mL of .300M chromium (II) fluoride reacts with excess zinc. How many grams of chromium are produced?
CrF2  +  Zn  -->  ZnF2  +  Cr

.250L  x  .300 mol  x 1  x  52.0g  =    3.9 g
                    L            1       mol

- how many moles of zinc flouride are produced?
.250L  x .300 mol  x  1  =    0.075 mol      
                    L            1

determine [ZnF2]  0.075 mol   x  1      =     0.3 M
                                                  0.250L

eg. A beaker contains 150 mL of 2.5 M HBr. Extra cadmium is added to the beaker.
Determine how many litres of hydrogen gas should be produced @ STP.

HBr  +  Cd   -->   H2   +   CdBr2

0.150 L  x  2.5 mol  x  1   x  22.4 L  =   4.2 L
                       L           2        mol
- if 2.50 L of hydrogen gas is actually produced what is the % yield?
                3.5 L  x  100  =  83%
                4.2 L

eg. A 4.50g piece of chromium is added to a beaker containing 300mL of 0.800 M RbNO3.
Determine L.R
Cr  +  2RbNO3   -->   2Rb  +   Cr(NO3)2

.300L  x  .800 mol  x  1   x   52.0g   =   6.34 g of Cr   (excess) 
                   L              2
                                                                 L.R =  RbNO3

posted by chemistry11 @ 10:34 PM