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Percentage of elements or empirical formula mass from combustion masses of CO2 and water

This type of question, asked 3 times: 2021 Paper 3, 14 Jun 2022, 2 Apr 2025. All 3 questions below, oldest first.

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  1. Question 1

    2021 Paper 3

    38
    Complete combustion of 1.80 g1.80\text{ }g of an oxygen containing compound (CxHyOz)\left( C_{x}H_{y}O_{z} \right) gave 2.64 g2.64\text{ }g of CO2CO_{2} and 1.08 g1.08\text{ }g of H2OH_{2}O. The percentage of oxygen in the organic compound is:

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  2. Question 2

    14 Jun 2022

    121
    120 g120\text{ }g of an organic compound that contains only carbon and hydrogen gives 330 g330\text{ }g of CO2CO_{2} and 270 g270\text{ }g of water on complete combustion. The percentage of carbon and hydrogen, respectively are.

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  3. Question 3

    2 Apr 2025

    42
    On complete combustion 1.0 g of an organic compound ( X ) gave 1.46 g of CO2CO_{2} and 0.567 g of H2OH_{2}O. The empirical formula mass of compound (X) is ___ g .(Given molar mass in gmol−1C:12,H:1,O:16gmol^{- 1}C:12,H:1,O:16 )

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