How does impurities affect percent yield

The actual yield is the amount of product that is actually formed when the reaction is carried out in the laboratory. The percent yield is the ratio of the actual yield to the theoretical yield, expressed as a percentage. Percent yield is very important in the manufacture of products.

Much time and money is spent improving the percent yield for chemical production. When complex chemicals are synthesized by many different reactions, one step with a low percent yield can quickly cause a large waste of reactants and unnecessary expense.

When a chemist synthesizes a desired chemical, he or she is always careful to purify the products of the reaction.

Potassium chlorate decomposes upon slight heating in the presence of a catalyst according to the reaction below:. During the purification stage some of the product may be lost in distillation, or by decomposition, or even evaporation.

Some may remain inside the reaction, or purification vessels, filtration systems, chromatographic columns etc etc. Higher than expected yield can only be due to the presence of impurities caused by inadequate purification.

It is usually because the product still contains solvent, but clearly it could still be mixed with other products or even reactants. The calculation is simple if you know the actual and theoretical yields. All you need to do is plug the values into the formula:. Usually, you have to calculate the theoretical yield based on the balanced equation.

In this equation, the reactant and the product have a mole ratio , so if you know the amount of reactant, you know the theoretical yield is the same value in moles not grams! You take the number of grams of reactant you have, convert it to moles, and then use this number of moles to find out how many grams of product to expect. Actively scan device characteristics for identification. Use precise geolocation data. Select personalised content. Create a personalised content profile.

Measure ad performance. Select basic ads. Create a personalised ads profile. An error when measuring the amount of educts for the reaction is one possible reason. A miscalculation at any point of the amounts needed or the final yield is also something you might want to check again.

A really common reason is the presence of other material in your product, often solvents like water are still present if you weren't careful enough when drying.

This is really the most likely cause, especially in student labs. You should think about the analytics you performed, and check if they show the presence of anything aside from your product. And then think about what kinds of substances could be in there solvents, educts, other reaction products that wouldn't be visible in the kind of analytics you performed. Such impurities could be present for many reasons, such as if the vessels used to collect the product are contaminated.

Also, it is possible that the product absorbs components from air like water vapor or carbon dioxide. Like others said, contaminants may be there or unreacted chemicals can be there.

It happened to one or two times while I was doing summer project and left the compound in vaccumm and a trap to get rid of solvents. You should use proper solvents to separate the product and unreacted or side product stuff.

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