Ch 9 Zumdahl
2/16/2016
NAME_____Key__________________
Chem 111- Quiz 7
Circle or box your final answers. Show your work.
1. (4 pts) For the following reaction, how many moles of the second reactant would be
required to react exactly with 0.275 moles of the first reactant?
Balance
1
Cl2(g) + __2__
KI(aq) 
___1__
I2(s) + ___2___ KCl(aq)
0.275 mol Cl2 x (2 mol KI/mol Cl2) = 0.550 mol KI
3 SIG FIGS! How is this anything other than 3 sig figs?!
2. (6 pts) How many grams of each product in the following reaction would be produced
by the complete reaction of 15.0 g of Cu2S?
2Cu2S(s) + 3O2(g)  2Cu2O(s) + 2SO2(g)
Molar masses:
Cu2S
O2
Cu2O
SO2
159.15
32.00
143.09
64.06
15.0 g Cu2S x (1 mol Cu2S/159.15 g Cu2S) = 0.09425 mol Cu2S
0.09425 mol Cu2S x (2 mol Cu2O/2 mol Cu2S) x (143.09 g Cu2O/mol Cu2O) = 13.5 g Cu2O
0.09425 mol Cu2S x (2 mol SO2/2 mol Cu2S) x (64.06 g SO2/mol SO2) = 6.04 g SO2
DON'T ROUND OFF IN THE INTERMEDIATE STEPS!