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Help me to answer these questions

  1. Nov 6, 2005 #1
    10 cm^3 of a gas G were mixed with 100 cm^3 (an axcess) of oxygen in a sealed container at 20 C and one atmosphere pressure . The gas was then ignited electrically and burned completely in the oxygen. After the reaction the volume of the gas mixture measured at the the same temperature & pressure , was found to be 105 cm^3. Which of the following was G?
    A CH4
    B H2
    c CO
    D C2H4

    and how??????

    10 cm^3 of a gaseous hydrocarbon needed 30 cm^3 of oxygen for complete combustion and 20 cm^3 of CO2 were produced . What is the molecular formula of the hydrocarbon and how?
    A CH4
    B C2H2
    C C2H4
    D C2H6

    In the thermit reaction :
    2Al + Cr2O3 produce 2Cr+ Al2O3
    Calculate the percentage yield when 180 g of chromium are obtained from a reaction between 100 g of aluminium and 400 g of chromium
    A sample of hydrated compound was analysed and found to contain 2.10g of cobalt , 1.14g of sulphur , 2.28g of oxygen and 4.50g of water. Calculate the emperical formula
    A 10.0g of a compound contained 3.91g of carbon , 0.87g of hydrogen and the reminder is oxygen. Calculate the emperical formula of the compound

    [ these questions are not difficult but there are some small problem make me not sure ]
  2. jcsd
  3. Nov 6, 2005 #2


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