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

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#### 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

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

Na2so4 Nacl and mgcl2
Should i count it wih formula of t=i*kb*b
b = molality
Kb = constanta
i = van hoff factor

#### 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.

#### 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

#### 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?

#### 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

#### 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?

#### 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

#### 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?

#### 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".

#### 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?

#### 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?

#### 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

#### 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

#### 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