September 16, 2019, 08:52:36 PM
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Topic: Question, dimensional analysis  (Read 162 times)

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Offline dja01

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Question, dimensional analysis
« on: September 05, 2019, 07:03:06 PM »
Came across this question on an exam today, completely blanked. Only question I wasn't confident in.

"I have a 33g sample of Potassium Sulfide, The atomic masses are K = 39, S = 32."

What is the molecular formula of Potassium Sulfide?

How many moles of Potassium are found when the 33g sample is dissolved in a .500 L solution?



This test was to be done without a calculator, and without a periodic table. I obviously knew that potassium sulfide is K2S, but is there something more to this question? For the second one, since there is no calculator allowed, I was just asked to set up the analysis, so i converted 33g of K2S to mol of K2S, and then used the mole ratio of 2 mol K to 1 mol of K2S. Can someone either confirm this or tell me where I went wrong?

Offline Borek

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Re: Question, dimensional analysis
« Reply #1 on: September 05, 2019, 07:32:03 PM »
Reasoning looks OK to me.

Calculations are reasonably easy even to do on paper or in memory.
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Offline dja01

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Re: Question, dimensional analysis
« Reply #2 on: September 05, 2019, 10:43:39 PM »
OK. Thanks!

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