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Chemistry LibreTexts

Homework 62

  • Page ID
    31003
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    Q 5.105:

    Question:

    • Write the empirical formula and molecular formula for the compound with the given percent composition and molecular weight.

    40.0% Carbon

    6.70% Hydrogen

    53.3% Oxygen

    Molecular Weight ≈ 240 g/mol

    Solution:

    Strategy:

    1. Calculate amount of grams of each element we have.

    2. Convert amount of grams into number of moles of each element.

    3. Obtain molecular formula.

    4. Find the common factor among the number of atoms each elements has, then obtain the empirical formula.

    Solution:

    1. Calculate amount of grams in each element:

    CodeCogsEqn.gif

    CodeCogsEqn-2.gif

    CodeCogsEqn-3.gif

    2. Convert amount of grams into number of moles of each elements:

    Carbon-

    CodeCogsEqn-4.gif

    Hydrogen-

    CodeCogsEqn-5.gif

    Oxygen-

    CodeCogsEqn-6.gif

    3. Obtain molecular formula:

    CodeCogsEqn-7.gif

    4. Find common factor and obtain empirical formula:

    Common factor is 4

    Empirical formula is

    CodeCogsEqn-8.gif


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