CHEM 141 (Watts). Fall 2008. Homework Assignment 8.
Due date and time: at final exam on Thursday, December 11, 2008.
Name: ________________________________
The following are multiple choice questions on stoichiometry problems (chapter 3). To
earn full credit, you must show your working on separate sheets of paper. Please write
clearly and neatly, showing appropriate work. Credit will not be given for illegible or
ambiguous work. Answers without appropriate working shown will not receive any
credit, even if they are correct.
The purpose of these questions is to provide further practice on problems of this type.
You are welcome to ask for help. My main concern here is for you to get some further
practice with problems of this type. There will be some questions of this general type on
the final exam.
1. What is the percent yield of the following reaction if 15 g of H2O are obtained
from the combustion of 18 g of C2H6?
2 C2H6 (g) + 7O2 (g) → 4 CO2 (g) + 6 H2O (l)
A. 46 g B. 67 g C. 54 g D. 40 g E. 23 g
2. Aluminum and bromine react vigorously as represented by the following
2 Al (s) + 3 Br2 (l) → 2 AlBr3 (s)
What mass of product can be made by reacting 5.0 g of aluminum and 22 g of
bromine?
A. 15 g B. 17 g C. 24 g D. 27 g E. 49 g
3. Aluminum and oxygen react according to the equation
4 Al (s) + 3 O2 (g) → 2 Al2O3 (s)
In a certain experiment, 4.6 g of aluminum was reacted with excess oxygen. If the
product was obtained in 64% yield, what was the mass of product obtained?
A. 2.9 g B. 1.5 g C. 8.7 g D. 5.6 g E. 65 g
[Note: this is asking for the actual yield. You will have to calculate the theoretical
yield first].
