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Difficulty: MediumOxides of Carbon and Trioxocarbonate(IV) Salts

A sample of 9.0 g9.0\text{ g} of anhydrous ethanedioic acid, H2C2O4\text{H}_2\text{C}_2\text{O}_4, is completely dehydrated using excess concentrated tetraoxosulfate(VI) acid. The evolved gaseous mixture is passed through an excess concentrated sodium hydroxide solution to absorb carbon(IV) oxide. What volume of pure carbon(II) oxide gas is collected at STP? [Molar mass of H2C2O4=90 g mol−1\text{H}_2\text{C}_2\text{O}_4 = 90\text{ g mol}^{-1}; Molar volume of gas at STP =22.4 dm3 mol−1= 22.4\text{ dm}^3\text{ mol}^{-1}]

  1. 2.24 dm32.24\text{ dm}^3Answer
  2. B
    2.40 dm32.40\text{ dm}^3
  3. C
    4.48 dm34.48\text{ dm}^3
  4. D
    4.80 dm34.80\text{ dm}^3

Answer

The volume of pure carbon(II) oxide collected at STP is 2.24 dm32.24\text{ dm}^3.
Dehydration of 9.0 g9.0\text{ g} (0.10 mol0.10\text{ mol}) of ethanedioic acid produces 0.10 mol0.10\text{ mol} of CO\text{CO} and 0.10 mol0.10\text{ mol} of CO2\text{CO}_2. Concentrated sodium hydroxide absorbs all the CO2\text{CO}_2, leaving only 0.10 mol0.10\text{ mol} of neutral CO\text{CO} gas. At STP (22.4 dm3 mol−122.4\text{ dm}^3\text{ mol}^{-1}), 0.10 mol0.10\text{ mol} of CO\text{CO} occupies 2.24 dm32.24\text{ dm}^3.

Step-by-Step Solution

1
Calculate the number of moles of ethanedioic acid (H2C2O4\text{H}_2\text{C}_2\text{O}_4).
Moles=9.0 g90 g mol−1=0.10 mol\text{Moles} = \frac{9.0\text{ g}}{90\text{ g mol}^{-1}} = 0.10\text{ mol}.
Determining initial mole quantity from given mass and molar mass.
2
Write the balanced chemical equation for the dehydration of ethanedioic acid.
H2C2O4(s)→conc. H2SO4CO(g)+CO2(g)+H2O(l)\text{H}_2\text{C}_2\text{O}_4(\text{s}) \xrightarrow{\text{conc. } \text{H}_2\text{SO}_4} \text{CO}(\text{g}) + \text{CO}_2(\text{g}) + \text{H}_2\text{O}(\text{l}).
1 mole of ethanedioic acid yields 1 mole of CO\text{CO} gas and 1 mole of CO2\text{CO}_2 gas.
3
Determine the mole amount of carbon(II) oxide collected after passing through sodium hydroxide.
Sodium hydroxide reacts with acidic oxide CO2\text{CO}_2 to form Na2CO3\text{Na}_2\text{CO}_3, leaving 0.10 mol0.10\text{ mol} of unreacted neutral CO\text{CO} gas to be collected.
Sodium hydroxide selectively absorbs carbon(IV) oxide, allowing pure carbon(II) oxide gas to pass through.
4
Calculate the volume of pure CO\text{CO} gas at STP.
\text{Volume} = 0.10\text{ mol} \times 22.4\text{ dm}^3\text{ mol}^{-1} = 2.24\text{ dm}^3$.
Converting moles of gas to volume at standard temperature and pressure.

Key Concept

Dehydration of ethanedioic acid yields an equimolar mixture of carbon(II) oxide and carbon(IV) oxide. Sodium hydroxide selectively absorbs carbon(IV) oxide, allowing pure carbon(II) oxide to be collected.
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Topics

Oxides of Carbon and Trioxocarbonate(IV) Salts

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