Chemistry Quiz: Theoretical Yield and Limiting Reactant

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The theoretical yield of products in a chemical reaction can be predicted from the stoichiometric ratios of the reactants and products of the reaction. These ratios can also be used to determine which reactant will be the first reactant to be consumed by the reaction. This reactant is known as the limiting reagent. These chemistry test questions deal with the subjects of theoretical yield and limiting reagent.

The answers appear after the final question. A periodic table may be required to complete the questions.

1. Evaporation

The minerals in seawater can be obtained through evaporation. For every liter of seawater evaporated, 3.7 grams of Mg(OH)2 can be obtained.

How many liters of seawater must be evaporated to collect 5.00 moles of Mg(OH)2?

2. Copper Production

Copper sulfate and zinc metal react to form zinc sulfate and copper by the reaction:

CuSO4 + Zn → ZnSO4 + Cu

How many grams of copper are produced from 2.9 grams of zinc consumed with excess CuSO4 in this reaction?

3. Carbon Dioxide Production

Sucrose (C12H22O11) combusts in the presence of oxygen to produce carbon dioxide and water by the reaction:

C12H22O11 + 12 O2 → CO2 + 11 H2O.

How many grams of CO2 are produced if 1368 grams of sucrose is combusted in the presence of excess O2?

4. Silver Sulfide Production

Consider the following reaction:

Na2S(aq) + AgNO3(aq) → Ag2S(s) + NaNO3(aq)

How many grams of Ag2S can be produced from 7.88 grams of AgNO3 and excess Na2S?

5. Silver Bromide Production

129.62 grams of silver nitrate (AgNO3) are reacted with 185.34 grams of potassium bromide (KBr) to form solid silver bromide (AgBr) by the reaction:

AgNO3(aq) + KBr(aq) → AgBr(s) + KNO3

a. Which reactant is the limiting reagent?
b. How much silver bromide is formed?

6. Excess Reagent

Ammonia (NH3) and oxygen combine to form nitrogen monoxide (NO) and water by the chemical reaction:

4 NH3(g) + 5 O2(g) → 4 NO(g) + 6 H2O(l)

If 100 grams of ammonia are reacted with 100 grams of oxygen

a. Which reagent is the limiting reagent?
b. How many grams of the excess reagent remains at completion?

7. Hydrogen Gas Production

Sodium metal strongly reacts with water to form sodium hydroxide and hydrogen gas by the reaction:

2 Na(s) + 2 H2O(l) → 2 NaOH(aq) + H2(g)

If a 50-gram

a. Which is the limiting reagent?
b. How many moles of hydrogen gas are produced?

8. Iron Production

Iron(III) oxide (Fe2O3) combines with carbon monoxide to form iron metal and carbon dioxide by the reaction:

Fe2O3(s) + 3 CO(g) → 2 Fe(s) + 3 CO2

If 200 grams of iron(III) oxide are reacted with 268 grams of carbon dioxide,

a. Which reactant is the limiting reactant?
b. How many grams of iron should be produced at completion?

9. Phosgene Neutralization

The poison phosgene (COCl2) can be neutralized with sodium hydroxide (NaOH) to produce salt (NaCl), water, and carbon dioxide by the reaction:

COCl2 + 2 NaOH → 2 NaCl + H2O + CO2

If 9.5 grams of phosgene and 9.5 grams of sodium hydroxide are reacted:

a. will all of the phosgene be neutralized?
b. If so, how much sodium hydroxide remains? If not, how much phosgene remains?

Answers

  1. 78.4 liters of seawater
  2. 2.8 grams of copper
  3. 2112 grams of CO2
  4. 5.74 grams of Ag2S
  5. a. silver nitrate is the limiting reagent. b. 143.28 g of silver bromide is formed
  6. a. Oxygen is the limiting reagent.
    b. 57.5 grams of ammonia remain.
  7. a. Sodium is the limiting reagent.
    b. 1.1 moles of H2
  8. a. Iron(III) oxide is the limiting reagent.
    b. 140 grams of iron
  9. a. Yes, all of the phosgene will be neutralized.
    b. 2 grams of sodium hydroxide remain.