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4.2: Limiting and Excess Reagents

Chem 1402:General Chemistry I · LibreTexts

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    Limiting Reagent

    Exercise \(\PageIndex{1}\)

    The box below shows a group of nitrogen and hydrogen molecules that will react to produce ammonia, NH3. What is the limiting reagent?

    fd7328fb16474b58c06ff92939b7ac6b.jpg

    Answer

    Nitrogen is the limiting reagent.

    Exercise \(\PageIndex{2}\)

    Given the statement “20.0 g of methane is burned in excess oxygen,” is it obvious which reactant is the limiting reagent?

    Answer

    Yes; methane is the limiting reagent.

     

    Calculations with Limiting Reagent

    Exercise \(\PageIndex{3}\)

    Acetylene (C2H2) is formed by reacting 7.08 g of C and 4.92 g of H2.

    2C(s) + H2(g) → C2H2(g)

    What is the limiting reagent? How much of the other reactant is in excess?

    Answer

    C is the limiting reagent; 4.33 g of H2 are left over.

    Exercise \(\PageIndex{4}\)

    To form the precipitate PbCl2, 2.88 g of NaCl and 7.21 g of Pb(NO3)2 are mixed in solution. How much precipitate is formed? How much of which reactant is in excess?

    Answer

    6.06 g of PbCl2 are formed; 0.33 g of NaCl is left over.

     

    4.2: Limiting and Excess Reagents is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts.