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Topic: Does this question make any sense?  (Read 3716 times)

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Offline is3zzz

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Does this question make any sense?
« on: September 22, 2007, 10:56:32 AM »
Question: What mass of 24.743 mass-% NaCl contains 60.35 grams of water? Error tolerance: ±0.5%

It doesn't seem possible to solve. Can anyone master this?
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Offline Yggdrasil

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Re: Does this question make any sense?
« Reply #1 on: September 22, 2007, 11:40:07 AM »
mass percent is a measure of concentration.  24.743% NaCl means that 24.743% of the total mass of the solution is NaCl.  For example, in 100g of solution, there are 24.743g of NaCl.
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Offline is3zzz

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Re: Does this question make any sense?
« Reply #2 on: September 22, 2007, 12:08:36 PM »
So does this mean that the answer to the mass is 39.65 grams?

Since water is 60.35 g which is can also be 60.35% of Water.  Therefore, 100-60.35= 39.65 grams.
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Offline sjb

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Re: Does this question make any sense?
« Reply #3 on: September 22, 2007, 12:21:10 PM »
Well, assuming you've water and NaCl and nothing else, then my reasoning would be as follows...

For every 100g total solution, you have 24.743g NaCl, and 100-24.743=75.257g water.

So for 60.35g water, you need 100 x 60.35/75.257g solution, which equals 80.192g (3dp) solution.

S
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