Rei asked in Science & MathematicsChemistry · 4 weeks ago

An A-level chemistry question?

10cm3 of ethane is burned in 45cm3 of oxygen at a pressure of 101 kPa and a temperature of 200C. Complete combustion takes place.

What is the total volume of gas present when the reaction is complete, measured under the same conditions?

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  • 4 weeks ago
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    10 mL of ethane is burned in 45 mL of oxygen at a pressure of 101 kPa and a temperature of 200ºC. Complete combustion takes place.

    Ethane + Oxygen ➜ Carbon Dioxide + Water

    2C₂H₆(g) + 7O₂(g) ➜ 4CO₂(g) + 6H₂O(g)

    2 mol C₂H₆(g) + 7 mol O₂(g) ➜ 4 mol CO₂(g) + 6 mol H₂O(g)

    volume of ideal gases at same temp and pressure is proportional to number of moles, so this is

    2 mL C₂H₆(g) + 7 mL O₂(g) ➜ 4 mL CO₂(g) + 6 mL H₂O(g)

    ratio of ethane to oxygen is 2/7 ... you have 10/45 or 2/9 ... so you have excess oxygen and ethane is controlling factor.

    2 mL of ethane results in 4+6 = 10 mL of product

    you have 10 mL of ethane so product is 50 mL

    plus there is leftover oxygen. 10(7/2) = 35 mL is used, leaving 10 mL

    so total volume = 60 mL

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