Question

Consider the following experimental error.

When measuring out the reactants, some copper II chloride was spilled on the balance and was not added to the reaction flask. How would this error affect your percent yield of Cu?

A) The mass that was spilled on the balance was not able to react and will not affect the percent yield.

B) The total recorded mass of the copper II chloride was not able to react which will cause a low percent yield (if it was the limiting reactant).

C) The mass of copper II chloride dihydrate will be recorded too high causing the percent yield to be high.

Answer 1

As it is given that while measuring some amount of reactant got spilled on balance and hence the balance will give the weight that is measured weight is less than the weight used during reaction.

Let the amount of reactant in flask is x

Amount spill is y

Therefore measured amount of reactant is x+y

Hence, the spilled amount of reactant is wasted and not used in reaction therefore yield will be low than expected.

Option B is correct. (Answer)

However option A state that spilled mass donot effect the percent yield which is not true as the yield obtained is less than expected.

Option C state that yield will be high which is definitely not true because the spilled mass is not used in reaction.