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21 May, 18:55

A 0.156 g piece of solid aluminum reacts with gaseous oxygen from the atmosphere to form solid aluminum oxide. In the laboratory, a student weighs the mass of the aluminum oxide collected from this reaction as 0.189 g.

What is the percent yield of this reaction?

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Answers (2)
  1. 21 May, 18:58
    0
    The percent yield of this reaction is 64.3 %

    Explanation:

    First of all we determine the reation:

    4Al (s) + 3O₂ (g) → 2Al₂O₃

    2nd step: we determine the moles (mass / molar mass)

    0.156 g / 26.98 g/mol = 0.00578 moles

    We assume O₂ as the excess reagent so the limiting is the Al

    Ratio is 4:2 so now we make a rule of three

    4 Al produce 2 moles of Al₂O₃

    Then 0.00578 moles of Al must produce (0.00578. 2) / 4 = 0.00289 moles of oxide.

    These moles are the 100 % yield reaction. Let' s convert the moles to mass

    0.00289 mol. 101.96 g / mol = 0.294 g

    This is the way to calculate the percent yield:

    (Produced yield / Theoretical Yield). 100 : (0.189 g / 0.294 g).100 = 64.3 %
  2. 21 May, 19:13
    0
    The percent yield of this reaction is 64.1 %

    Explanation:

    Step 1: Data given

    Mass of solid aluminium = 0.156 grams

    Mass of aluminium oxide produced = 0.189 grams

    Atomic mass of aluminium = 26.98 g/mol

    Molar mass of aluminium oxide = 101.96 g/mol

    Step 2: The balanced equation

    4Al + 3O2 → 2Al2O3

    Step 3: Calculate moles aluminium

    Moles aluminium = mass aluminium / molar mass aluminium

    Moles aluminium = 0.156 grams / 26.98 g/mol

    Moles aluminium = 0.00578 moles

    Step 4: Calculate moles aluminium oxide

    For 4 moles aluminium we need 3 moles O2 to produce 2 moles Al2O3

    For 0.00578 moles aluminium we'll have 0.00578/2 = 0.00289 moles aluminium oxide

    Step 5: Calculate mass of aluminium oxide

    Mass Al2O3 = moles Al2O3 * molar mass Al2O3

    Mass Al2O3 = 0.00289 moles * 101.96 grams

    Mass Al2O3 = 0.295 grams

    Step 6: Calculate percent yield

    % yield = (actual yield / percent yield) * 100%

    % yield = (0.189 grams / 0.295 grams) * 100 %

    % yield = 64.1 %

    The percent yield of this reaction is 64.1 %
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