Question

When 22.4 litres of ${H_2}$ (g) is mixed with 11.2 litres of Cl2 (g), each at STP, the moles of HCl (g) formed is equal to:
A. 1 mol of HCl (g)
B. 2 mol of HCl (g)
C. 0.5 mol of HCl (g)
D. 1.5 mol of HCl (g)

Answer 1

The given problem is related to the concept of stoichiometry of chemical equations. Thus, we have to convert the given volume into their moles and then identify the limiting reagent. The limiting reagent gives the moles of product formed in the reaction.

Complete step by step answer:
from Avogadro’s law it is known that equal volumes of all gases contain equal numbers of molecules under similar conditions. Now since one mole of molecules of all gases contain the same number (6.022$\times {10^{23}}$ ) of molecules, therefore they occupy the same volume under similar pressure and temperature. The mass of one mole of atoms is exactly equal to the atomic mass in grams of that element. From the above question we have to calculate when 22.4L of ${H_2}$ reacts with 11.2L of $C{l_2}$ at standard temperature and pressure to form HCl gas then the number of moles we have to calculate will be, where we know that at STP one mole of any gas occupies a volume of 22.4L.
The balanced equation to the above question is
${H_2} + C{l_2} \to 2HCl$
We can conclude that 1mole of ${H_2}$ reacts with one mole of $C{l_2}$ to give 2 moles of HCl. ($C{l_2}$) chlorine is the limiting reagent in the reaction as it is the reactant species which limits the formation of products.. Since we are given with the volume of the reactants we will convert it into the number of moles that will react by using the concept of mole and molar volume as explained above.
11.2L volume will be occupied by, $C{l_2}$ =$\dfrac{{1 \times 11.2}}{{22.4}} = 0.5$ moles
1 mol $C{l_2}$= 2 x0.5 mol = 1.0 mol HCl (Hence, 0.5 moles of chlorine will form 1 mole of HCl)
1mole of $C{l_2}$forms 2 mole of HCl
Thus when 22.4 litres of ${H_2}$ is mixed with 11.2 L of $C{l_2}$, each at STP the moles of HCl formed is equal to 1 mole of HCl.
Hence the correct option is option A.

Note:
A limiting reagent in a reaction is the species supplied in an amount smaller than that required by the stoichiometric relation between the reactants. In the above reaction limiting reagent is chlorine. Always write a balanced equation in the questions of stoichiometry.