Confusing Stoichiometry Question

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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)).
 

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  • #2
DrClaude
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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)
That is much too low. Please show your calculations.

(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?
 
  • #3
Borek
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2,738
That is much too low. Please show your calculations.
I got 7.051 g as well:

 
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  • #4
DrClaude
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I'm sorry for the mistake. I used the density of Cl2 given by WolframAlpha, which is much higher.
 
  • #5
Borek
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28,352
2,738
Looks like they are listing density of a liquid Cl2 - which doesn't make much sense at STP....
 
  • #6
DrClaude
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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...
 

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