Question

Define the following term Limiting reagent

Answer 1

Reagent can be a substance or mixture of compounds which are used in chemical analysis or reactions. When a reagent is added to a system it causes chemical reactions. For a particular reaction, a particular reagent gets consumed in the process of the chemical reaction.

Complete step by step solution:
Now, the limiting reagent of a reaction is that reagent which gets consumed totally in the reaction. That is after the reaction the amount of that reagent in the reaction mixture will be zero. The amount of limiting reagent consumed is proportional to the amount of product formed.
Limiting reagents can be calculated in several ways. One of the useful ways is, to compare the mole ratios of the reagent amounts which are used. It can also be calculated by comparing the amount of product that can be formed from each reactant of a reaction.
When 76.4 grams of ${C_2}{H_3}B{r_3}$ reacts with 49.1 grams of ${O_2}$ . The following reaction has occurred.
$4{C_2}{H_3}B{r_3} + 11{O_2} \to 8C{O_2} + 6{H_2}O + 6B{r_2}$ .
Now, according to this reaction. For 49.1 grams of ${O_2}$ which is equal to 1.53 moles of ${O_2}$ require 0.556 moles of ${C_2}{H_3}B{r_3}$ . But here, 76.4 grams of ${C_2}{H_3}B{r_3}$ is equal to 0.286 moles of ${C_2}{H_3}B{r_3}$ .
So, here ${C_2}{H_3}B{r_3}$ will be consumed totally in this reaction. So here ${C_2}{H_3}B{r_3}$ is the limiting reagent.

Note:
To distinguish between one compound from another use reaction where the change of physical characteristics has happened. For example, change of color of the solution, precipitation takes place, generation of effervescence, etc. Tollen’s reagent reacts with only terminal alkyne compounds, not with all alkynes. It also can be used to distinguish between a terminal alkyne and non-terminal alkyne. Therefore, using tollens reagent you can distinguish between a terminal alkyne and non-terminal alkynes.