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28 May, 00:51

A certain compound has the percent composition (by mass) 85.63% C and 14.37% H. The molar mass of the compound is 42.0 g/mol. Calculate the empirical formula and the molecular formula.

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  1. 28 May, 01:00
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    The molecular formula is C3H6

    Explanation:

    Step 1: Data given

    Suppose the compound has a mass of 100 grams

    The compound contains:

    85.63 % C = 85.63 grams C

    14.37 % H = 14.37 grams H

    Molar mass C = 12.01 g/mol

    Molar mass H = 1.01 g/mol

    Step 2: Calculate moles

    Moles = grams / molar mass

    Moles C = 85.63 grams / 12.01 g/mol

    Moles C = 7.130 moles

    Moles H = 14.37 grams / 1.01 g/mol

    Moles H = 14.2 moles

    Step 3: Calculate the mol ratio

    We divide by the smallest amount of moles

    C: 7.130 moles / 7.130 moles = 1

    H = 14.2 moles / 7.130 moles = 2

    The empirical formula is CH2

    The molar mass of CH2 = 14 g/mol

    Step 4: Calculate molecular formula

    We have to multiply the empirical formula by n

    n = 42 / 14 = 3

    n * (CH2) = C3H6

    The molecular formula is C3H6
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