Question

Which of the following statements best describes a limiting reactant?

Answer 1

Answer:

c. The reactant that is used up before the others  

Explanation:

b. is also correct, because the limiting reactant is completely used up.

a. and d. are wrong. They describe the excess reactant.

Answer 2

Answer: c. The reactant that is used up before the others

Explanation:

For example:

$2HCl+Ca\rightarrow CaCl_2+H_2$

If we are given 100 g of $HCl$ and 100 g of calcium.

As can be seen from the chemical equation, 2 moles of hydrochloric acid react with 1 mole of calcium.

According to mole concept, 1 mole of every substance weighs equal to its molar mass.

Thus $2\times 36.5=73 g$ of of hydrochloric acid reacts with 40 g of calcium.

100 g of hydrochloric acid react with=$\frac{40}{73}\times 100=54.79 g$of calcium

Thus HCl is the limiting reagent as it limits the formation of product and calcium is the excess reagent as (100-54.79)=45.21 g is left unreacted.

Thus HCl which is a limiting reagent will be used up before Calcium.