11 Grade Chemistry

Chemistry – Mrs. Wright

Answer the following 15 questions as you study this week’s lessons. The spaces will expand as you type in your answers. This is a study guide and may not include all the things that you study for this week but it is a good place to start. 2015-2016 SM2

Lesson 23: Stoichiometry

1. Stoichiometry problems use all of the following, except one. Which one is NOT involved in stoichiometry?

a. mass of reactants or products

b. number of moles of reactants or products

c. amount of time it takes for a reaction to occur

d. a balanced equation must be used to solve stoichiometry problems

2. When the lesson pages talk about a mole ratio between two substances, what does that mean? Where do the numbers for the mole ratio come from?      

3. One mole of Aluminum may be represented as 1 mol or       grams or       atoms.

4. Short essay question. Why is a balanced chemical equation needed to solve a stoichiometry problem?      

5. Consider the reaction of combining hydrogen and nitrogen to produce ammonia.

The balanced equation is: 3H2 + N2 ➜ 2NH3

a. What is the mole ratio of hydrogen to nitrogen?      

b. What is the mole ratio of hydrogen to ammonia?      

c. What is the mole ratio of nitrogen to ammonia?      

6. Consider the equation HCl + Al AlCl3 + H2.

a. Is this equation balanced?      

b. Balance it. _ HCl + _ Al _ AlCl3 + _ H2

7. Use the balanced equation in #6b above. How many moles of hydrogen would be produced if you used 12 moles of HCl and enough Al to completely react?      

8. In your own words, explain one of the methods used, (either from Mr Hunyady’s video explanations, or the other method from the stoichiometry lesson) of how to find the amount of grams of a product from a given amount of moles of a reactant? This is an essay question. Please use an example to show how it works.

Lesson 24: Limiting Reagents

9. Explain what we mean by a limiting reagent. Use an everyday example to show what this means.      

10. Suppose you are going to make sandwiches that contain 2 pieces of bread, 2 slices of ham, 3 slices of turkey, 2 leaves of lettuce and 2 pieces of cheese. If you have a total of 60 pieces of bread, 40 slices of ham, 30 slices of turkey, 50 leaves of lettuce and 20 pieces of cheese, how many sandwiches can you make?      

11. In the sandwich problem above, how many pieces of ham would be left over after making all the sandwiches you could?      

12. What is the limiting reagent (or ingredient) in this sandwich problem? (Is there more than one?)      

13. Describe, in your own words, what is meant be each of these terms:

a. actual yield      

b. theoretical yield      

c. percent yield      

14. Why would chemists not get a 100% yield on a reaction they run in a laboratory?      

15. If a student calculates that he should get exactly 400.0 g of a certain product but in the lab, he only gets 285 g, what is the percent yield for the reaction?