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Topic: Percent By mass  (Read 6360 times)

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Offline quest10

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Percent By mass
« on: July 18, 2009, 03:31:38 PM »
Hello,

I hope that someone can help shed some light with this question that I have.  I am very bad when it comes to math so word problems are a nightmare for me.  The question is:

A Solution contains 15.0 g of NH4Cl in water and is 8.50% NH4CL.  What is the mass of water present?

I don't have any examples of how to do this, so I am not sure where to start.  I was thinking that the percent of water would be 91.5% but I am not sure if I should multiply the molar mass of H2O by 91.5?  If you could help me with this, that would be great.

Thanks

Quest10
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Offline keyser_soze

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Re: Percent By mass
« Reply #1 on: July 18, 2009, 04:38:42 PM »
is it 8.50 mol% ammonium chloride? or weight?
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Offline nameless74

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Re: Percent By mass
« Reply #2 on: July 18, 2009, 05:06:53 PM »
15.0 multiply by a 100% and divide 8.50%
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Offline quest10

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Re: Percent By mass
« Reply #3 on: July 18, 2009, 05:25:58 PM »
Thanks for your help.  I was told that the answer is 161.5g is that incorrect?  If I do it the way you explained I get 176.5g.
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Offline Borek

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Re: Percent By mass
« Reply #4 on: July 18, 2009, 05:32:16 PM »
Quote from: quest10 on July 18, 2009, 03:31:38 PM
A Solution contains 15.0 g of NH4Cl in water and is 8.50% NH4CL.  What is the mass of water present?

What is the definition of mass percentage?
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Offline Borek

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Re: Percent By mass
« Reply #5 on: July 18, 2009, 05:33:20 PM »
Quote from: nameless74 on July 18, 2009, 05:06:53 PM
15.0 multiply by a 100% and divide 8.50%

No.
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Offline quest10

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Re: Percent By mass
« Reply #6 on: July 18, 2009, 05:46:30 PM »
The text book says that percent by mass expresses the mass of solute per 100 grams of solution
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Offline Borek

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Re: Percent By mass
« Reply #7 on: July 18, 2009, 07:04:40 PM »
What formula do you use to calculate it?

Write the formula and check what you know and what you are looking for. Mass of solution is mass of solvent plus mass of solute. Can you solve for mass of the solvent?
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Offline Sameerchand

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Re: Percent By mass
« Reply #8 on: July 21, 2009, 11:07:07 AM »
A Solution contains 15.0 g of NH4Cl in water and is 8.50% NH4CL.  What is the mass of water present?

Hello.. here is an answer that might be correct.

Edit: Please read forum rules. Don't do homework for others.
« Last Edit: July 21, 2009, 11:37:37 AM by Borek »
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