What Is Percent Yield And How To Calculate It? (With Examples)

By Sky Ariella - Jul. 26, 2022
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When taking the pharmaceuticals that bring us back to full health, we rarely stop to think about what went into making them. Before becoming a tiny white pill that obliterates a headache in a matter of hours, a series of chemical processes took place first to create it – under the observation of a trained chemist.

During creation, chemical reactions take place in these products, which provide a specific amount of usable results. Post-reaction, chemists use a formula called percent yield to calculate how much product they should have derived theoretically versus the amount they actually obtained.

Key Takeaways:

  • Percent yield is the percentage of an actual result to an expected result and reveals the success of the situation in question.

  • The formula for percent yield is: (Actual Yield / Theoretical Yield) X 100 = Percent Yield.

  • Percent yield is used in chemistry to evaluate how successful a chemical reaction was in reality, compared to the maximum result expected.

  • Percent yield can also be used by different disciplines when comparing actual results to expected results.

What Is Percent Yield And How To Calculate It? (With Examples)

What Is Percent Yield?

Percent yield is a formula used by chemists in the process of evaluating chemical reactions. For every chemical reaction they deal with, there is an expected result. Even with an anticipated result in mind that should happen chemically, this doesn’t end up being the case the vast majority of the time.

The percent yield formula shows the chemist a percentage of how successful the reaction was in reality, compared to the maximum result they were expected.

The formula for percent yield is:

(Actual Yield / Theoretical Yield) X 100 = Percent Yield

Why Is Percent Yield Important?

While the percent yield formula is used to better understand chemical reactions, it’s also valuable for other reasons, such as finances. A company that creates a chemically-based product uses the percent yield formula to evaluate their finances and productivity in product creation.

A low percent yield describes a reaction that is extremely far off from the expected result. That means that the production is being completed inefficiently. A lack of productivity destroys even the strongest companies because it wastes money and time.

What Is Theoretical Yield?

Theoretical yield refers to the maximum possible mass of a product that can be made as a result of a chemical reaction. Using stoichiometry, chemists are able to determine precisely how much should result, however actual chemical reactions almost never occur exactly as these formulae predict.

There are unavoidable experimental errors, side reactions, or incomplete chemical reactions in the real world. Companies that deal in chemical production of any sort have a huge interest in eliminating these factors as much as possible to achieve a yield as close to the theoretical yield as possible.

How to Calculate Percent Yield

With a basic understanding of what the percent yield value is demonstrating after a chemical reaction, it’s time to get into how to break down the somewhat unnerving formula, piece by piece.

Below are the steps for how to calculate the percent yield.

  1. Understand the formula. To begin any math problem from basic addition to advanced trigonometry, start by taking in the formula. Although mathematical and chemical formulas are dreadful when you’re unsure of what every portion means, they’re much more straightforward after analyzing each piece of the puzzle.

    In the percent yield formula, two values need to be figured out and plugged in. These are the actual yield and the theoretical yield.

  2. Find the value of the actual yield. The actual yield is the result that was achieved from this rendition of the chemical reaction. Regardless of what science says should happen, this value is what actually did happen.

  3. Find the value of the theoretical yield. The theoretical yield is the expected result after a reaction. Chemistry explains it as the maximum anticipated result.

    This could mean a lot of different things depending on what chemical medium you’re working with. For example, how long it takes a chemical substance to dissipate after being heated at a particular temperature.

    The theoretical yield of a particular reaction can be uncovered with research.

  4. Divide the theoretical yield by the actual yield. Once the values of actual yield and theoretical yield are discovered, following through with the rest of the equation becomes fairly easy.

    The actual yield should go on the top of the division, and the theoretical yield goes on the bottom. Insert each value into its respective place in the division and solve. This leaves you with a decimal that represents the unrefined percent yield.

  5. Multiply the result by 100. With the decimal form of the percent yield answer, the last thing to do is multiply this result by 100. After multiplication, a whole number is formed. This is the percent yield.

Examples of Calculating Percent Yield

Percent Yield Example 1:

A chemist is observing the reaction of potassium carbonate (K₂CO₃) to produce soap for a large manufacturer. In this particular test, he’s timing how long the inorganic compound takes to dissolve under a heat lamp pushing out temperatures of 37 degrees celsius.

The theoretical yield of this reaction is 17 minutes. When the experiment is performed, the actual yield ends up being 13.2 minutes. He needs to find the percent yield of this particular chemical reaction to report back to the soap manufacturer on the process’s productivity.

He reviewed the equation for percent yield, which is:

(Actual Yield / Theoretical Yield) X 100 = Percent Yield

He already knows the values of the reactions’ actual yield and theoretical yield. He plugs those values into the equation. The equation now looks like this:

(13.2. / 17) X 100 = Percent Yield

Next, he divides the theoretical yield by the actual yield. He does this action first because this function is between parentheses.

The result of the division is 0.776. This is the unrefined percent yield of the reaction.

The equation now looks this:

0.776 X 100 = Percent Yield

Finally, the chemist multiples the unrefined percent yield by 100 to get the final percent he needs to pass along to the soap manufacturer. The result of this is 77.6%. This is the percent yield.

What it means: In a laboratory setting, it’s nearly impossible to create the perfect sequence of chemical reactions to achieve the theoretical maximum yield. Generally, any percent yield value over 60% is considered effective and fairly impressive.

Since the percent yield for this equation was 77.6%, this describes a result that was close to the theoretical yield, which means it’s productive.

Percent Yield Example 2:

A major healthcare company produces hydrogen peroxide (H2O2), a chemical compound made up of hydrogen and oxygen used to clean out small cuts and scrapes. The company wants to conduct an experiment concerned with the decomposition of hydrogen peroxide to understand their processes’ effectiveness.

The theoretical yield of the hydrogen peroxide decomposition is 54.3. After measuring the actual yield during the reaction, it is 23.7. The company’s chemist puts this information in the percent yield formula in the appropriate places.

(23.7 / 54.3) X 100 = Percent Yield.

The chemist divides 23.7 by 54.3 to arrive at the unrefined percent yield value of 0.436.

He multiples this decimal value by 100 to get the actual percent yield.

0.436 X 100 = 43.6

The percent yield is 43.6%.

What it means: This percent yield result isn’t nearly as encouraging as the one from the previous example. As stated earlier, any percent yield over 60% is generally considered to be positive productivity. 43.6% is clearly under this standard. However, this value isn’t necessarily terrible.

It isn’t until a percent yield value is lower than 40% that it’s thought of as poor and unacceptable in terms of efficiency. While the percent yield result of 43.6% is cutting it very close to being negative, it is still considered acceptable.

Final Thoughts

Percent yield is an important element for chemical manufacturers around the world. The lower this number drops, the more the company is wasting on reactants. Not to mention the time wasted on inefficient processes.

Note that while we’ve been discussing actual yield as always lower than theoretical yield, it is possible for your percent yield to be greater than 100%. This can happen if the reactants are impure and unexpected side reactions occur. When the percent yield is greater than 100%, it’s equally concerning for manufacturers as when their percent yield is below 60%.

Even if you’re not a chemist, knowing what goes into production costs and affects the bottom line can make you a more savvy contributor to your team.

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Sky Ariella

Sky Ariella is a professional freelance writer, originally from New York. She has been featured on websites and online magazines covering topics in career, travel, and lifestyle. She received her BA in psychology from Hunter College.

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