Consider the reaction between H3PO4(aq) and Al2(CO3)3(s) to form CO2(g), H2O(l) and AlPO4(s).

Question

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If the percent yield of CO2(g) is 64.0% and the theoretical yield of CO2(g) is 67.0 grams, determine the amount of CO2(g) formed in the reaction.

Answer 1

You're given a percent yield and a theoretical yield, and being asked to find the actual yield. These are the three elements of the percent yield formula, which is:

actual yield

———————— • 100

theoretical yield

Plug in your values.

x grams

————— • 64.0 %

67.0 grams

In order to do the calculation, convert your percentage to a decimal by dividing by 100, or moving the decimal to spaces to the left. That'll give you .640

Since you're trying to find the numerator, you multiply the denominator by the percentage.

.640 • 67.0 = 42.9 (rounded to three significant digits)

A quick check to make sure you did the math correctly: Your actual yield will never be higher than your percent yield. In this case, your actual yield was a bit over 50%, and 42.9 is a bit more than half of 67.0.