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Confusing Stoichiometry Question

by pure kirk
Tags: confusing, stoichiometry
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pure kirk
#1
Sep15-13, 10:34 AM
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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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DrClaude
#2
Sep15-13, 01:49 PM
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Quote Quote by pure kirk View Post
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.

Quote Quote by pure kirk View Post
(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
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Sep16-13, 04:57 PM
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Quote Quote by DrClaude View Post
That is much too low. Please show your calculations.
I got 7.051 g as well:


DrClaude
#4
Sep16-13, 05:15 PM
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Confusing Stoichiometry Question

I'm sorry for the mistake. I used the density of Cl2 given by WolframAlpha, which is much higher.
Borek
#5
Sep17-13, 02:26 AM
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Looks like they are listing density of a liquid Cl2 - which doesn't make much sense at STP....
DrClaude
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Sep17-13, 02:35 AM
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Quote Quote by Borek View Post
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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