Unit 8 ReviewStoichiometry

Complete on Markerboard or

in your notes.

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.

2. How many grams of sodium nitrate are formed if 20.0 g of Na3N are reacted with excess silver nitrate?

Na3N (aq) + 3 AgNO3 (aq) Ag3N (s) + 3 NaNO3 (aq)

3. How many liters of carbon monoxide are needed to react with 4.85 g of oxygen gas to produce carbon dioxide? DCO = .0958 g/L.

Equation:

4. What mass of ammonia, NH3, is necessary to react with 2.15 x 1024 molecules of oxygen in the following equation?

____ NH3(g) + ____ O2(g) ____ H2O(g) + ____NO2(g)

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-overs are called Excess Reactants (ER).

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 CuNO3 (aq) 2 Cu (s) + Zn(NO3)2 (aq)

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

Use the reaction to determine the limiting reactant in the following scenarios?

O2 + 2 NO 2 NO2

7. 4 molecules O2 reacts with 6 molecules NO ___________

8. 1 mole O2 reacts with 3 moles NO ___________

9. 5 moles O2 reacts with 7.00 moles NO ___________

10. 10.00 g O2 reacts with 20.00 g NO ___________ * You must calculate this one!

NO

O2

NO

O2

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.•

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…

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) + ____ O2 (g) ____ MgO (s)

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 (Fe2O3) are formed? ____ FeS (s) + ____ O2 (g) ____ Fe2O3 (s) + ____ SO2 (g)

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

16. 3.74 g of copper is formed when 1.87 g of aluminum reacts with excess of copper (II) sulfate.

2Al (s) + 3 CuSO4 (aq) Al2(SO4)3 (aq) + 3Cu (s)

• calculate the theoretical yield

• calculate the percent yield

• calculate the experimental error.

*Must turn in your packet with notes stapled to it