Question

What effect on your calculated yield would the following experimental errors have had?

A) Incomplete evaporation of the excess hydrochloric acid

B) Excessive heating of the product to cause decomposition (say to manganese(II) oxide)

C) Cooling the product in the open air (especially on a humid day)

D) Which of the above errors are the most probable?

Experiment: Manganese sample is dissolved in concentrated HCl, exess HCl and water will be evaporated to obtain solid manganese(II) chloride.

Answer 1

Answer A)

Incomplete evaporation of HCl will lead to sticking of acid on the product. This will add on to the mass of product and hence calculated yield would be more than actual yield.

Answer B)

Excessive heating may cause the product to decompose. Decomposition will increase the mass of solid but the actual product will be less. So, it will also cause the calculated yield to be more than the actual yield.

Answer C)

In humid day, the water will not evaporate easily and hence will remain sticking to the product. This will cause increase in calculated yield.

Answer D) Most probable is the over heating of product. It is because, aqueous HCl is difficult to evaporate and overheating may occur.