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Topic: Colligative problems  (Read 1699 times)

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Offline nawinince

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Colligative problems
« on: June 05, 2018, 08:51:33 AM »
(1) 9.0 g of C6H12O6, was dissolved in 100 g of water. The freezing point of the glucose solution was determined to be -0.94°C. Determine the molar freezing-point depression of water in the unit of (K kg/mol)

my attempt :

molal = (9/180)/100*10^-3 = 1/2

T=k*molal

0.94 = K*1/2
K=1.88

but the answer is 1.9

what did i miss?

Offline sjb

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Re: Colligative problems
« Reply #1 on: June 05, 2018, 10:24:16 AM »
Nothing really (sig fig? units?)

Offline nawinince

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Re: Colligative problems
« Reply #2 on: June 05, 2018, 10:04:26 PM »
Nothing really (sig fig? units?)

So my solution was correct? if so, my question must has mistake.

Offline Borek

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Re: Colligative problems
« Reply #3 on: June 06, 2018, 02:46:12 AM »
So my solution was correct? if so, my question must has mistake.

Your calculations are OK, you just reported too many significant digits (you were expected to round down the 1.88 to 1.9).

https://en.wikipedia.org/wiki/Significant_figures
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