CHEMISTRY COMMUNITY

What are some reasons why the actual yield for an experimental reaction is not equal to the theoretical yield? Do we need to be prepared to explain why this happened if given a lab scenario?

Actual yields will be less than theoretical yields due to side reactions that can occur, some products could stick to the sides of the reaction container, and impurities that are bound to happen during almost all chemical reactions. Hope this was helpful/answered your question!

You should be familiar with this concept :)

Can't the theoretical yield also be higher than the actual yield? For example if you incorrectly weighed something or there were impurities in the final product, then the mass would increase and be greater.

I think it is not plausible for theoretical yield to be less than the actual yield because if you weighed something wrong, that just means you got a wrong theoretical yield.

The actual yield for an experimental reaction is not equal to the theoretical yield because of side reactions that occur as well as impurities in the container that might hinder the reaction. Additionally, no reaction is ever 100% complete since the reactants don't completely react with each other, unless circumstances are perfect--which never occurs.

Another way to look at why the actual yield is less than the theoretical yield is to consider finding percent yield.

Recall that percent yield is equal to the actual yield divided by the theoretical yield multiplied by 100%.

Since the actual yield is in the numerator, this implies that the theoretical yield must be larger in order to make a decimal. If the numerator was larger, there would be a decimal larger than 1, which would result in a percent yield over 100%, which does not happen. Thus, mathematically, the numerator (the actual yield) must be smaller than the denominator (the theoretical yield).

Theoretical yield is the amount of product that can be obtained if a chemical reaction has 100% efficiency, the maximum amount of yield possible. Actual yield is the amount of product actually produced by the reaction. Due to side reactions, impurities, some of the product sticking on to the sides of the beaker, etc., the actual product tends to be less than the theoretical yield.

Benjamin Feng 4B wrote:Can't the theoretical yield also be higher than the actual yield? For example if you incorrectly weighed something or there were impurities in the final product, then the mass would increase and be greater.

Yes the theoretical yield is higher than the actual yield since the theoretical yield represents the reaction if it were 100% efficient.

Theoretical yield will never be higher than actual yield. Theoretical yield is the result if the reaction is 100% efficient and there are no impurities or errors during the experiment. Theoretical yield represents the maximum yield.

Actual yield is less than theoretical yield due to experimental errors such as sticking to the sides, incomplete reactions, or loss of the sample.

Actual yield is different than theoretical yield due to error in lab. Sometimes, side reactions will occur or if there are impurities in the reactants. You should be familiar with at least one reason in case needed to explain on the test.

The actual yield is less than the theoretical yield because impurities can occur, like products getting stuck to the side of the beaker.

the actual yield will have to be less than the theoretical yield due to impurities and more that will occur in an actual reaction!

The actual yield is to take into account the flaws that could occur in an experiment. Human error could offset the expected results, or the theoretical yield.

The actual yield is to take into account the flaws that could occur in an experiment. Human error could offset the expected results, or the theoretical yield.

There could either be a difference due to human error or experimental flaws that are somewhat unavoidable such as side reactions.

There could either be a difference due to human error or experimental flaws that are somewhat unavoidable such as side reactions.

A theoretical yield determines the max amounts a reaction can produce because it only assumes the variables and amounts being presented in a given problem; this is similar to a physics problem about velocity or acceleration where simplified equations consider amounts in a vacuum while not taking into account variables such as friction or wind resistance. A theoretical yield doesn't take into account side reactions which may burn off chemicals or impurities in a given experiment hence the actual yield is less than the theoretical yield.

Theoretical yield is the maximum amount of product you could get out of a reaction. I don't think actual yield can ever be more than theoretical. Products can get stuck in the beaker and tubes when doing a reaction or measuring, so it will be less than the maximum. Then you can divide the actual yield by theoretical yield and get a percentage to see how efficient the reaction is.

emaad_3H wrote:What are some reasons why the actual yield for an experimental reaction is not equal to the theoretical yield? Do we need to be prepared to explain why this happened if given a lab scenario?

The theoretical yield for an experiment would normally be greater than the actual yield for an experiment, this could be due to errors... systematic error or random error. It also makes sense that the theoratical yield would greater than actual yield because that would be given a perfect scenario and lab settings and all of the reagents react perfectly and the frequency of effective collisions and total amount of reagents used would equal the amount of product produced with no wastage, but in real-life even in lab settings this is hard to attain and random errors although can be minimized with proper lab techniques and procedures can still occur.

emaad_3H wrote:What are some reasons why the actual yield for an experimental reaction is not equal to the theoretical yield? Do we need to be prepared to explain why this happened if given a lab scenario?

Also this formula is important for calculating percentage yield = ( Actual Yield/ Theoratical Yield X 100%)

Hope this helps! (:

Well, actual yield is the mass of the product that was actually obtained while theoretical is just going to be what is expected, without any complications or opportunities for the mass of the product to decrease. So normally, the actual yield will always be less than the calculated theoretical due to impurities, side reactions, incomplete reactions, and etc.

The theoretical yield is what you're supposed to get if there are no errors or other factors that affect the experiment. However sometimes factors such as the experiment sticking to the side of the test tube will reduce the amount of yield (actual yield).

HannahBui 3I wrote:Actual yields will be less than theoretical yields due to side reactions that can occur, some products could stick to the sides of the reaction container, and impurities that are bound to happen during almost all chemical reactions. Hope this was helpful/answered your question!

exactly ! There are almost always offshoots of some kind in experiments whether it be any of the latter as stated. Even if minimal and very small, it does affect the actual yield outcome .

The theoretical yield is the amount produced when a reaction is completed with 100% efficiency. The actual yield is the amount that is actually produced by the reaction.

The theoretical yield is what you would obtain in perfect conditions where the reactants are pure. However, during an experiment, side reactions could occur, the reactants could stick to the walls of the container, decreasing the amount of reactants that are reacting, or impurities in the container in which the reaction occurs could affect the amount of products obtained. Therefore, there usually is a difference between the theoretical yield and the actual yield.

The actual yield is generally not equal to the theoretical yield because of impurities during experimentation or other factors such as solution staying on the sides of the beaker. In order for the actual yield to equal the theoretical yield, the experiment would need to be executed perfectly.

I understand the theoretical yield will always be greater than the actual yield due to substances sticking the the side of the beaker, etc, but are there ways to minimize or calculate this difference? And is it possible to have a theoretical yield that is exactly equal to the actual yield?

How do you calculate the actual yield and theoretical yield?

If given the values of the other terms, you could simply solve the equation for the missing value.

For example: if solving for actual yield, the question would likely provide the values of theoretical yield and percent yield, so you can solve for actual yield by multiplying the theoretical yield by the percent yield.

We calculate theoretical yield based on the limiting reagent. We use however many moles of the LR and the molar ration of the balanced equation to determine how much product we could make under perfect conditions. Actual yield needs to be given in the question, since we don't know it without doing the experiment ourselves. Percent yield tells us how efficient the reaction is.

Like any experiment, there are always side reactions that can occur such as loss of heat, impurities (product sticks to the side of the beaker), or human error (incorrect measurements of reactants). Taking these things into account, the actual yield is going to be less than the theoretical yield because we have to account for these errors

The actual yield is less than the theoretical yield due to impurities and side reactants. I don't believe it's a concept you'll have to justify in the lab. You just need to familiarize yourself with it.

theoretical yield is the yield that will be obtained if all of the given reactants are used to completion and everything goes perfectly. However during real experiments, more often than not, things happen; the product sticks to the beaker, escapes into the atmosphere or something, and the yield obtained will be less than the theoretical. This yield is the actual yield.

E.g., the scale is off, your measurement is not perfectly precise, some of the reactants evaporate during the reaction.

The actual yield will most of the time be less than the theoretical yield because of competing reactions, measurement errors, and/or limiting reactants. The theoretical yield is the maximum quantity of product that can be obtained from a chemical reaction.

It is common for actual yield to be less than theoretical yield due to human error or device error. Substances can stick to containers, things can be measured incorrectly, etc.

Actual yield is less than theoretical due to almost unavoidable mistakes, for example, slight inaccuracies in measuring out reactants or some of the product sticking to the side of the beaker when measuring. Theoretical yield is the largest possible yield in a reaction, as it assumes there are no mistakes or inaccuracies when the reaction occurs.

A lot of reactions or system cannot be 100% efficient because there are always something that is lost to the environment, uncontrollable variables that can alter the result, side reaction, and impurities. Those are just some of the reasons why actually yield is almost always less than the theoretical yield in a reaction.