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14.9A: Oxides and Oxoacids of Carbon

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    34190
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    Carbon Monoxide

    • A colorless and very dangerously toxic gas - it has no smell - boiling point -190 oC.
    • It is thermodynamically unstable with respect to carbon and carbon dioxide, but the equilibrium is only established at high temperature:

      \[\ce{2CO(g) -> C(s) + CO2(g)}\]

    • An important primary industrial chemical, involved in several reaction sequences:

      \[\ce{CH4 + 2H2O -> CO2 + 4H2}\]

      \[\ce{C + H2O -> CO + H2 (+ H2O) "water gas"}\]

      \[\ce{CO + H2O -> CO2 + H2} \tag{"water gas shift" reaction}\]

      Mixtures of carbon monoxide and hydrogen are called "synthesis gas" or "syngas".

    • Formally CO is the anhydride of formic acid, HCCH, but CO does not react at room temperature with water.
    • Carbon monoxide is unique in that it is a weak Lewis base (s-donor through carbon) but a very strong p-acceptor. Asa ligand it stabilizes transition metals in low zero or negative oxidation states.

    Carbon Dioxide and Carbonic Acid

    • Carbon dioxide makes up about 0.03% (300 ppm) of the earth's atmosphere. It is mainly produced from volcanic activity, fermentation of organic matter and fires of al types.
    • Solid carbon dioxide sublimes at -78 oC at atmospheric pressure, making it a useful refrigerant ("dry ice").
    • Carbonic acid H2CO3 is produced only very slowly when CO2 is dissolved in water. The equilibrium constants usually quoted are:

    \[\dfrac{[\ce{H^{+}}]\{\ce{HCO3^{-}}\}}{[\ce{H2CO3}]} = 4.16 \times 10^{-7}\]

    \[\dfrac{[\ce{H{+}}][\ce{CO3^{2-}}]}   {[\ce{HCO3^{-}}]} = 4.84 \times 10^{-11}\]

    but the first is incorrect because the real [H2CO3] is much lower than what is calculated based on dissolved CO2. The real constant is probably closer to 2x10-4 more in keeping with a compound with a C=O bond - see Chapter 7 section 12.


    14.9A: Oxides and Oxoacids of Carbon is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by LibreTexts.

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