H2(g)+Cl2(g)2HCl(g)+. If 2 mol of hydrogen gas are mixed with 4 mol of chlorine gas, how many moles of hydrogen chloride will be produced?

1 Answer
Mar 30, 2017

4 moles of HCl are produced

Explanation:

The ratio at which the compounds react with each other are displayed in a chemical reaction as the numbers in front of the compounds. For example in this reaction:

1 H2 molecule reacts with 1 Cl2 molecule
Forming
2 HCl molecules.

In chemistry moles are used as a handy number of a certain amount of stuff. You can compare this to a dozen eggs, which is always 12. In the same way 1 mol is the number 6.0221023. This number tells us how many particles there are. So in 1 mol there are 6.0221023 particles. This number is also referred to as the constant of Avogadro.

In the question the amount of moles for H2 and for Cl2 are given. We have to calculate how much HCl is produced with both these values. Therefore 2 calculations needs to be done.

Because moles just tells us something about the amount of particles we can use the ratio of the reaction to calculate how many HCl will be produced.

We start of with the 2 moles of hydrogen gas. We know the following now:
1 mole of H2 gives 2 moles of HCl
Therefore
2 moles of H2 gives 4 moles of HCl

Now this same calculation can be done for the Cl2:
1 mole of Cl2 reacts to 2 moles of HCl, therefore
4 moles of Cl2 reacts to 8 moles of HCl.

Now we see we have 2 different amount of moles for HCl and the question now is which one should we use?
We must now look at which one of above reactions can occur? So for the 2 moles of H2, we can calculate with the ratio that:
2 moles of H2 reacts with 2 moles of Cl2.
We do have 2 moles of Cl2 available!

Let's see the other one
4 moles of Cl2 reacts with 4 moles of H2
But we do not have 4 moles of H2!!

Therefore we can only make 4 moles of HCl instead of 8 moles.

This situation can be stated as following: The Cl2 is abundant.