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2.4.3: Reaction Stoichiometry (Problems)

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    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

    Click here to see a video of the solution

    *Apologies for the brief phone ringing*

    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

    Click here to see a video of the solution

    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?

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


    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.


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

    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?


    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?

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


    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)


    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).


    1.28 × 105 g CO2

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