IGCSE Chemistry

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Hydrocarbons A and B both contain 85.7 % carbon. Their molar masses are 42 and 84 respectively.
a) Which elements does a hydrocarbon contain?
b) Calculate the empirical formula of A and of B.
c) Calculate the molecular formula of A and B.


I solved a) and b)

the solutions are
a) Hydrogen and Carbon
b) the simplest ratio is 2:1 so empiral formula is CH2

  • IGCSE Chemistry -

    For a C mass fraction of 0.857 = 12/14, the C:H ratio must be 1:2

    c) Let the formula be CnH2n
    For A, the molar mass is
    42 = n*12 + (2n)*1 = 14 n, so
    n = 3
    The formula of A is C3H6

    B has twice as many atoms of each.

  • IGCSE Chemistry -

    Thanks

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