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Topic: Order the one has highest boiling point to lowest  (Read 2799 times)

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Offline Helly

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Order the one has highest boiling point to lowest
« on: November 15, 2019, 04:22:08 AM »
1 g each of these dissolve in 1 L water
1. Glucose
2. Sodium chloride
3. Sodium sulfate
4. Magnesium chloride

My answer :
Glucose is the lowest, due to covalent bonding with no hydrogen forces not ionic

Na2so4 Nacl and mgcl2
But what about these 3?
Should i count it wih formula of t=i*kb*b
b = molality
Kb = constanta
i = van hoff factor


Offline mjc123

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Re: Order the one has highest boiling point to lowest
« Reply #1 on: November 15, 2019, 04:30:27 AM »
Quote
Should i count it wih formula of t=i*kb*b
Yes. Same for glucose - ionic vs. covalent is irrelevant - and it does have hydrogen bonding.

Offline AWK

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Re: Order the one has highest boiling point to lowest
« Reply #2 on: November 15, 2019, 04:34:01 AM »
according to your formula t/kb=i*b should show the highest value. Compare all i*b values.
AWK

Offline Helly

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Re: Order the one has highest boiling point to lowest
« Reply #3 on: November 15, 2019, 06:20:27 AM »
After i calculated, i get nacl = 0.035, and mgcl2 = 0.0315, so highest is nacl
But the answer isnt nacl, why?

Offline AWK

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Re: Order the one has highest boiling point to lowest
« Reply #4 on: November 15, 2019, 06:44:48 AM »
From the question:
"Order the one has the highest boiling point to lowest"
I understand that the answer should be:
eg.) 1>3>2>4 or 1,3,2,4
AWK

Offline Helly

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Re: Order the one has highest boiling point to lowest
« Reply #5 on: November 15, 2019, 06:54:01 AM »
Tell me how to conclude that?

Offline AWK

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Re: Order the one has highest boiling point to lowest
« Reply #6 on: November 15, 2019, 07:03:30 AM »
Order - the highest boiling point  - to lowest
AWK

Offline Helly

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Re: Order the one has highest boiling point to lowest
« Reply #7 on: November 15, 2019, 07:14:48 AM »
Tell me how do i decide which one is higher and lower?

Offline mjc123

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Re: Order the one has highest boiling point to lowest
« Reply #8 on: November 15, 2019, 08:13:27 AM »
You were on the right lines before. @AWK is simply pointing out that the question doesn't say "which is highest?" but "put them in order".

Offline Helly

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Re: Order the one has highest boiling point to lowest
« Reply #9 on: November 15, 2019, 08:27:33 AM »
Ok. But the highest isnt nacl, why is it wrong then?

Offline Helly

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Re: Order the one has highest boiling point to lowest
« Reply #10 on: November 15, 2019, 09:01:44 AM »
From my calculation nacl is bigger than mgcl2, but why the answer mgcl2 has higher boil point than nacl?

Offline Borek

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Re: Order the one has highest boiling point to lowest
« Reply #11 on: November 15, 2019, 09:23:22 AM »
Must be an error, I got the same numbers as you did for NaCl and MgCl2 and your conclusion that NaCl has the highest boiling point looks OK.

Technically i for MgCl2 will be lower than 3 due to the ion association, whether you should account for that or nor depends on the course level. If that is a HS course i=3 is a reasonable first approximation.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Offline Helly

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Re: Order the one has highest boiling point to lowest
« Reply #12 on: November 15, 2019, 09:34:58 AM »
Really? Thanks borek and all

Offline AWK

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Re: Order the one has highest boiling point to lowest
« Reply #13 on: November 16, 2019, 03:42:16 AM »
Four months ago there was an analogous question (using 10 g of substances)  with the same wrong answer: magnesium chloride
https://chemistry.stackexchange.com/questions/118229/which-one-has-the-highest-boiling-point

Please, give the source of your problem
AWK

Offline Helly

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Re: Order the one has highest boiling point to lowest
« Reply #14 on: November 16, 2019, 04:18:48 AM »
Yes. I found it but i already posted here. What do i do by "give source of problem"

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