# Confusing Stoichiometry Question

## Main Question or Discussion Point

I got this question as an example question and I have no clue on how to solve part B

Chlorine can be produced by the reaction:
2KMnO4 + 16HCl ->2KCl + 2MnCl2 + 5Cl2 + 8H2O
(a)What mass of KMnO4 is required to produce 2.5 L of Cl2 gas measured at STP?

For part A I got 7.05 g ( 0.044615 moll)
(b) Calculate the volume of commercial hydrochloric acid required (Commercial grade hydrochloric acid is 36.0% HCl by weight, and has a density of 1.18 g mL^(–1)).

DrClaude
Mentor
I got this question as an example question and I have no clue on how to solve part B

Chlorine can be produced by the reaction:
2KMnO4 + 16HCl ->2KCl + 2MnCl2 + 5Cl2 + 8H2O
(a)What mass of KMnO4 is required to produce 2.5 L of Cl2 gas measured at STP?

For part A I got 7.05 g ( 0.044615 moll)

(b) Calculate the volume of commercial hydrochloric acid required (Commercial grade hydrochloric acid is 36.0% HCl by weight, and has a density of 1.18 g mL^(–1)).
Can you start by figuring what mass of HCl you need?

Borek
Mentor
I got 7.051 g as well:

Last edited by a moderator:
DrClaude
Mentor
I'm sorry for the mistake. I used the density of Cl2 given by WolframAlpha, which is much higher.

Borek
Mentor
Looks like they are listing density of a liquid Cl2 - which doesn't make much sense at STP....

DrClaude
Mentor
Looks like they are listing density of a liquid Cl2 - which doesn't make much sense at STP....
Indeed. Very strange.

I feel ashamed because I didn't follow the rule that I always tell my students: when you get a numerical answer, always try to figure out if the order of magnitude makes sense. I should've checked with the ideal gas law...