Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: KungKemi on October 03, 2016, 01:27:38 AM
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Similar to a previous post, I also came across the following stoichiometry question in an RSC journal:
"A mixture contains KClO, MnCl2 and KMnO4. What must the percentage of potassium be to have the chlorine percentage equal to the percentage of oxygen?"
I have been working this question through for quite a while now and have come up with the following 5 systems:
39.10a + 39.10c = x
54.94b + 54.94c = y
35.45a + 70.9b = z
16.00a + 64.00c = z
x + y + 2z = 100
As can be seen, I have a total of 6 unknowns: a = mol KClO, b = mol MnCl2, c = mol KMnO4, x = mass of K,
y = mass of Mn, and z = mass of O or mass of Cl.
Nonetheless, since I only have 5 unique expressions; the following question is unsolvable with the method which I am currently using.
I was just wondering if I was missing something or if the following question is indeed unsolvable?
n.b. I mainly want to know if the following question is solvable. I do not want to have any hints. ;)
Thank you,
KungKemi
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Solution exists, but it is not what you think it is.
You definitely started right by writing system of equations, but you are expecting wrong kind of a solution.
No need to use colors in posts, they are perfectly readable in black.
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Solution exists, but it is not what you think it is.
You definitely started right by writing system of equations, but you are expecting wrong kind of a solution.
No need to use colors in posts, they are perfectly readable in black.
Okay, thank you Borek. Also, I was wondering if you would be able to share the answer which you arrive at (just so I can compare my answer in future if I arrive at one), as the source where I found this question does not list solutions.
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If you look at KClO, it contains lower mass of oxygen then mass of chlorine. KMnO4 contains only oxygen without chlorine. It means you can prepare mixture of both salts that fulfill requirement that mass of O equals to mass of Cl (equivalent to %O=%Cl). After addition of MnCl2 you should increase oxygen by adding more KMnO4.
Hence this is multisolution problem.
Check my reasoning starting from 1 mole of KClO and calculate how many moles of KMnO4 (without addition of any MnCl2) fulfills condition: %O=%Cl.