2.4.3: Reaction Stoichiometry (Problems)

PROBLEM \(\PageIndex{1}\)

Write the balanced equation and determine the information requested. Don't worry about state symbols in these reactions.

1. The number of moles and the mass (in grams) of chlorine, Cl₂, required to react with 10.0 g of sodium metal, Na, to produce sodium chloride, NaCl.
2. The number of moles and the mass (in milligrams) of diatomic oxygen formed by the decomposition of 1.252 g of mercury(II) oxide.
3. The number of moles and the mass (in g) of sodium nitrate, NaNO₃, required to decompose and produce 128 g of diatomic oxygen, where NaNO₂ is the other product.
4. The number of moles and the mass (in kg) of carbon dioxide formed by the combustion of 20.0 kg of carbon in an excess of diatomic oxygen.
5. The number of moles and the mass (in kg) of copper(II) carbonate needed to decompose in order to produce 1.500 kg of copper(II) oxide, where CO₂ is the other product.
6. The number of moles and mass (in grams) of C₂H₄ required to react with water to produce 9.55 g C₂H₆O.

Answer a

\(\ce{2Na}+\ce{Cl2}\rightarrow \ce{2NaCl}\)

0.217 mol Cl₂

15.43 g Cl₂

Answer b

\(\ce{2HgO}\rightarrow \ce{2Hg}+\ce{O2}\)

0.00289 mol O₂

92 mg O₂

Answer c

\(\ce{2NaNO3}\rightarrow \ce{2NaNO3}+\ce{O2}\)

8 mol NaNO₃

680 g NaNO₃

Answer d

\(\ce{C}+\ce{O2}\rightarrow \ce{CO2}\)

1666.67 mol CO₂

73.3 kg CO₂

Answer e

\(\ce{CuCO3}\rightarrow \ce{CuO}+\ce{CO2}\)

18.87 mol CuCO₃

2.330 kg CuCO₃

Answer f

\(\ce{C2H4}+\ce{H2O}\rightarrow \ce{C2H6O}\)

0.207 mol C₂H₄

5.81 g C₂H₄

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PROBLEM \(\PageIndex{2}\)

I₂ is produced by the reaction of 0.4235 mol of CuCl₂ according to the following equation: \(\ce{2CuCl2 + 4KI \rightarrow 2CuI + 4KCl + I2}\).

1. How many molecules of I₂ are produced?
2. What mass of I₂ is produced?

Answer a

1.28 × 10²³ molecules I₂

Answer b

53.8 g I₂

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PROBLEM \(\PageIndex{3}\)

Silver is often extracted from ores as K[Ag(CN)₂] and then recovered by the reaction

\(\ce{2K[Ag(CN)2]}(aq)+\ce{Zn}(s)\rightarrow \ce{2Ag}(s)+\ce{Zn(CN)2}(aq)+\ce{2KCN}(aq)\)

1. How many molecules of Zn(CN)₂ are produced by the reaction of 35.27 g of K[Ag(CN)₂]?
2. What mass of Zn(CN)₂ is produced?

Answer a

5.337 × 10²² molecules

Answer b

10.41 g Zn(CN)₂

PROBLEM \(\PageIndex{4}\)

What mass of silver oxide, Ag₂O, is required to produce 25.0 g of silver sulfadiazine, AgC₁₀H₉N₄SO₂, from the reaction of silver oxide and sulfadiazine?

\(\ce{2C10H10N4SO2 + Ag2O \rightarrow 2AgC10H9N4SO2 + H2O}\)

Answer

8.12 g Ag₂O

PROBLEM \(\PageIndex{5}\)

Carborundum is silicon carbide, SiC, a very hard material used as an abrasive on sandpaper and in other applications. It is prepared by the reaction of pure sand, SiO₂, with carbon at high temperature. Carbon monoxide, CO, is the other product of this reaction. Write the balanced equation for the reaction, and calculate how much SiO₂ is required to produce 3.00 kg of SiC.

Answer

\(\ce{SiO2 + 3C \rightarrow SiC + 2CO}\)

4.50 kg SiO₂

PROBLEM \(\PageIndex{6}\)

Automotive air bags inflate when a sample of sodium azide, NaN₃, is very rapidly decomposed.

\(\ce{2NaN3}(s) \rightarrow \ce{2Na}(s) + \ce{3N2}(g)\)

What mass of sodium azide is required to produce 2.6 ft³ (73.6 L) of nitrogen gas with a density of 1.25 g/L?

Answer

142g NaN₃

PROBLEM \(\PageIndex{7}\)

Urea, CO(NH₂)₂, is manufactured on a large scale for use in producing urea-formaldehyde plastics and as a fertilizer. What is the maximum mass of urea that can be manufactured from the CO₂ produced by combustion of 1.00×10³ kg of carbon followed by the reaction?

\[\ce{CO2}(g)+\ce{2NH3}(g)\rightarrow \ce{CO(NH2)2}(s)+\ce{H2O}(l)\]

Answer

5.00 × 10³ kg Urea

PROBLEM \(\PageIndex{8}\)

In an accident, a solution containing 2.5 kg of nitric acid was spilled. Two kilograms of Na₂CO₃ was quickly spread on the area and CO₂ was released by the reaction. Was sufficient Na₂CO₃ used to neutralize all of the acid? (in this reaction, water and sodium nitrate are the other two products)

Answer

No, you will need 2.1 kg of sodium carbonate to neutralize 2.5 kg of nitric acid.

PROBLEM \(\PageIndex{9}\)

A compact car gets 37.5 miles per gallon on the highway. If gasoline contains 84.2% carbon by mass and has a density of 0.8205 g/mL, determine the mass of carbon dioxide produced during a 500-mile trip (3.785 liters per gallon).

Answer

1.28 × 10⁵ g CO₂

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Contributors and Attributions

• Paul Flowers (University of North Carolina - Pembroke), Klaus Theopold (University of Delaware) and Richard Langley (Stephen F. Austin State University) with contributing authors. Textbook content produced by OpenStax College is licensed under a Creative Commons Attribution License 4.0 license. Download for free at http://cnx.org/contents/85abf193-2bd...a7ac8df6@9.110).

• Adelaide Clark, Oregon Institute of Technology

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