My grandmother left me some silver years ago. I opened the box containing the silver and it had tarnished. Using the equation below, if I had 300 g of silver that had tarnished and 175g H2S, which would be the limiting reactant? 2 Ag (s) + H2S (g) → Ag2S (s) + H2 (g) A. hydrogen B. silver C. There is no limiting reactant in this case D. hydrogen sulfide E. silver sulfide

B

Explanation:

The limiting reagent in a chemical reaction is the one that is consumed completely in the course of the reaction. It dictates the extent to which the reaction would proceed as the completion of the reaction is based solely on it.

There are several ways to determine the limiting reagent. The easiest way to do this that works is to divide the number of moles of each reagent by their stoichiometric coefficient in the balanced equation. The reactant with the least value is the limiting reagent.

Thus, we need to calculate the number of moles of silver and hydrogen sulphide. To do this, we simply divide the masses by the relative atomic masses or molecular masses.

The atomic mass of silver is 108.

The number of moles of silver is =

300/108 = 2.8

We now divide this by the stoichiometric coefficient: 2.8/2 = 1.4

We do same for hydrogen sulphide. The molar mass of hydrogen sulphide is 34g/mol

The number of moles is thus 175/34 = 5.15

We now divide this by stoichiometric coefficient = 5.15/1 = 5.15

We can see that silver has less number of the value and hence it is the limiting reactant.