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Percent Yield definition

A chemical reaction consists of two main entities; reactants and products. Yield is the quantity of the total amount of product synthesized due to a chemical reaction in relation to the quantity of consumed reacting mixture. A chemical reaction has many chemical factors or conversion factors depending upon its nature. It is always represented in percentage.

In chemistry, we deal with three different types of yield as follows.

Related: Learn complete process of how to balance redox reactions in basic medium.

  • Theoretical yield - It is the total amount of product predicted from the balanced equation of the corresponding chemical reaction. For example, you predict that you will score 80% in your next chemistry exam, then this 80% is your theoretical yield of effort.
  • Actual yield - It is the total amount of product that is actually obtained after the reaction. For example, you thought about scoring 80% in an exam but got 78%, then it is your actual yield.
    Since some mass gets converted to energy during the reaction, the actual yield is always lesser than the theoretical one.
  • Percent yield - It is the ratio of theoretical yield to the actual yield. If a chemical reaction gives a similar actual and theoretical yield, its percent yield will always be 100%.

Related: Bond formation and reaction between sodium and chloride.

How to Calculate Percent Yield of a Reaction Step by Step?

You can find the percent yield of chemical reactions using 4 simple steps. These steps are:

Step 1: Understand the requirements

In order to calculate percent yield equation, first we need to understand the requirements. As stated before, the theoretical yield is always higher than that of the actual yield.

The reason is the failure of some reactants to change into products due to various factors like unforeseen problems, the presence of contaminants, and mass-energy conversion. The percent yield definition tells the ratio of both these types of yield, which helps us to calculate percent yield of chemical reactions.

Going further, we will use the percent yield formula for calculating the percent yield equation. The percentage yield formula is:

Percent yield = Theoretical yield ÷ Actual yield × 100

The percent yield formula makes it easy for us to learn how to find percent yield. To get the value of percentage yield, you need to find out the values for theoretical and actual yield first and just putting in in the percent yield formula. If the percent yield of a reaction is 60%, then it means that you got the actual yield equal to 60% of your theoretical yield.

Related: Find what is synthesis in chemistry with examples.

Step 2: Calculate the Actual Yield

For calculating percent yield, first you have to calculate the actual yield. If you are performing the chemical reaction by yourself, then there will be no problem in calculating the actual yield. You have to weigh your product using a balance and note the value of the total product mass.

You can also balance your equations using online chemical equation balancer on the home page of this website.

Step 3: Calculate the Theoretical Yield

The third step in finding the percentage yield is to calculate the theoretical yield of chemical reaction. There are two main methods to find the theoretical yield of a reaction. The one used to find theoretical yield at the industrial level and the other that is used to calculate theoretical yield at more minor levels (for few moles).

For this purpose, all you have to do is to multiply the number of moles with the molar mass of each reactant and then sum up all the values together, such as

2H2 + O2 - - - > 2H2O

2(2) + 2(16) = 36g

Thus, the theoretical yield of water produced by the reaction of two moles of hydrogen and one mole of oxygen will be 36g.

CO + 2H2 - - - > CH3OH

Suppose you have been asked to find the theoretical yield of methyl hydroxide produced by 1.2 tons of hydrogen gas. At the same time, the amount of CO left even after the completion of the reaction.

Related: Complete process of a metal displacement reaction in an aqueous medium with different examples.

It is clear from the problem that the limiting reactant is hydrogen since CO is still present in excess amounts after the end of the reaction. Now, let's find the molar masses of each entity of the reaction medium, such as

Molar mass of CO2 = 28g

Molar mass of 2H = 4g

Molar mass of CH3OH = 28+4 = 32g

In the final step, multiply the actual mass (used) of hydrogen with the molar mass ratio of the final product and limiting reagent such as

1.2 tons 2H2 = 32g CH3OH ÷ 4g 2H2 = 9.6 tons

Thus, the theoretical yield of methyl hydroxide produced from 1.2 tons of hydrogen is 9.6 tons.

  • Finding theoretical yield at smaller levels
  • Finding theoretical yield at the industrial level

Related: Learn about gas laws and their importance in real life. Also learn how to find the oxidation state of an element in a compound.

Step 4: Add the Values in the Percent Yield Formula

Suppose you have been asked to calculate the percent yield of a reaction whose theoretical yield is 95g while the actual yield is 92.2g. To get percent yield, insert the values in the percent yield formula, So the percent yield equation will be

Percent yield = Theoretical yield ÷ Actual yield × 100

Percent yield = 92.2g ÷ 95g × 100 = 97.0%

This is how we can find percent yield and calculate percent yield equation.

Related: A detailed article to learn about history and importance of periodic table.

Importance of Percent Yield

Percent yield shows the efficiency of a chemical reaction or a complex chemical reaction. A company that manufactures different chemical compounds determines whether a reaction is profitable or not using percent yield definition.

For example, a chemical reaction possessing a low percent yield will not be favorable since the company has to spend more money to purchase the reactants than the amount it would earn from selling the resulting product. In a nutshell, lower productivity rates waste both money and time, which can even destroy a well-established enterprise in just a few months.

Frequently Asked Questions

Why is it important to calculate the percent yield in a chemical reaction?

It is important to calculate the percent yield in a chemical reaction because it shows the efficiency of a chemical reaction. Percentage yield is calculated to compare the actual yield quantity of a product. This help us to identify whether all of the reactants are converted with no loss or waste.

Can the percent yield of a chemical reaction be more than 100?

In most of the cases, percentage yield of a chemical reaction is less than 100%. It can go upto 100% only if the measure product has impurities. Because the impurities can cause the mass to be greater than it actually would be.

What relationship is used to determine the percent yield of a chemical reaction?

Relationship that is used to determine the percent yield of a chemical reaction is that we calculate the ratio of actual yield to theoretical yield.

What does percent yield represent in a chemical reaction?

Percen yield in a chemical reaction represents the percentage of the anticipated yield which is actually produced. The formula for percent yield is:

Percent yield = Theoretical yield ÷ Actual yield × 100

I hope this article helped you a lot in learn some useful things regarding different kinds of yield. There are also many useful articles in the blog section which you can read. Find the article and learn how to determine head of combustion in organic chemistry.