Question

a.) Can the percent yield be increased by increasing the amount of limiting reagent? Explain your answer.

b.) Why was the nickel chloride hex a hydrate dissolved in the minimum possible amount of water?

c.) Why can a percent yield might be less than 100% and greater than 100%?

Answer 1

a) The limiting reactant is defined as the reactant which decides the yield of the product. The percent yield is defined as the ratio of the actual mass of the product obtained to the theoretical yield. The actual mass of the product obtained is definitely decided by the amount of the limiting reactant. Hence, increase in the amount of the limiting reactant can certainly improve the actual mass of product obtained and hence, the percent yield. However, it must be noted that all other conditions must be conducive for the reaction to progress efficiently.

b) Need to know the complete experiment.

c) The percent yield of a reaction is most often less than 100. This is due to the fact that a reaction involves a number of steps and loss of intermediates and products is common in any chemical reaction. Moreover, it may also turn out that the reaction is not particularly efficient, i.e, one of the reactants doesn’t completely react to form the product.

The percent yield of a reaction can turn out to be greater than 100 and this usually happens due to carelessness on the part of the experimenter. Improper washing or drying of products can lead to moisture being trapped in the product and register a greater yield. A more common occurrence is the presence of impurities with the desired product. This will increase the actual mass of product obtained and hence, the percent yield.