1. Unit 8 Review Stoichiometry

2. 1. Describe how a chemist uses stoichiometry? To determine the amount of reactants needed or products formed based on the amount of another reactant or product.

3. 2.How many grams of sodium nitrate are formed if 20.0 g of Na 3 N are reacted with excess silver nitrate? Na 3 N (aq) + 3 AgNO 3 (aq)  Ag 3 N (s) + 3 NaNO 3 (aq)

4. 4.What mass of ammonia, NH 3, is necessary to react with 2.15 x 10 24 molecules of oxygen in the following equation? ____ NH 3 (g) + ____ O 2 (g)  ____ H 2 O(g) + ____NO 2 (g)

5. 5. What is a limiting reactant? How does a LR affect a reaction? What do you call the left-over chemicals? Limiting reactant is the reactant that is used up first. LR being used up stops the reaction and determines how much product can form. Left-over chemicals are called Excess Reactants (ER).

6. 6. If 75.00 grams of zinc metal and 100.0 grams of copper (I) nitrate react, how many grams of copper metal will be produced according to the following equation? What is the limiting reactant? Zn (s) + 2 CuNO 3 (aq)  2 Cu (s) + Zn(NO 3 ) 2 (aq)

7. Accelerated Only: How many grams of excess reactant are left over?

8. Use the reaction to determine the limiting reactant in the following scenarios? O 2 + 2 NO  2 NO 2 7. 4 molecules O 2 reacts with 6 molecules NO___________ 8. 1 mole O 2 reacts with 3 moles NO___________ 9. 5 moles O 2 reacts with 7.00 moles NO ___________ 10. 30.0 g O 2 reacts with 30.0 g NO ___________ NO O2O2

9. 11.What is percent yield? What does it tell you about a reaction? What is the equation for percent yield? Ratio of grams actually formed to grams that should have formed. Describes the efficiency of a reaction.

10. 12. How does the actual yield of a chemical reaction compare to the theoretical yield? Why? The actual yield of a reaction is measured in a lab and theoretical yield is calculated. They are different because of lab errors, contamination, inefficient reactions, etc…

11. 13.Burning 20.0 grams of magnesium metal produces 32.5 grams of solid product. What is the percent yield for this reaction? ____ Mg (s) + ____ O 2 (g)  ____ MgO (s)

12. 14. 10.0 grams of iron (II) sulfide is reacted according to the following equation. The percent yield is 97.25%. How many grams of rust (Fe 2 O 3 ) are actually formed? ____ FeS (s) + ____ O 2 (g)  ____ Fe 2 O 3 (s) + ____ SO 2 (g)

13. 15. A student carried out this experiment in the lab by reacting 22.4 g of oxygen with excess hydrogen and 24.5 g of water were formed. What is the percent yield

14. 16.3.74 g of copper is formed when 1.87 g of aluminum reacts with excess of copper (II) sulfate. 2Al (s) + 3 CuSO 4 (aq)  Al 2 (SO 4 ) 3 (aq) + 3Cu (s) calculate the theoretical yield calculate the percent yield calculate the experimental error.