G7 - Homework Problem

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RahilVaknalliDis3A
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G7 - Homework Problem

Postby RahilVaknalliDis3A » Tue Oct 03, 2017 11:03 pm

You need to prepare 510 g of an aqueous solution containing 5.45% of KNO3 by mass. Describe how you would prepare the solution and what mass of each component would you use.

Is there a specific reaction we need to know about? I managed to calculate the mass of water and salt using the information.

Chem_Mod
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Re: G7 - Homework Problem

Postby Chem_Mod » Tue Oct 03, 2017 11:18 pm

There is no reaction you need to know for this, as it is solution preparation. You must solve for the mass of water and mass of KNO3 and mixing the two should yield the 510 grams of solution with 5.45% KNO3 by mass.

Michael Lee 2I
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Re: G7 - Homework Problem

Postby Michael Lee 2I » Tue Oct 03, 2017 11:29 pm

First you find the mass of KNO3, which is the percentage (5.45%) x the total mass of the aqueous solution (510g). Then you need to find the mass of the water before the KNO3 is added to it which is the total mass of the aqueous solution (510g) subtracted by the mass of KNO3.
So to prep the solution you would start with a beaker of just H20 and then add in the KNO3 and mix it until it dissolves.

Jana Sun 1I
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Re: G7 - Homework Problem

Postby Jana Sun 1I » Thu Oct 05, 2017 11:18 pm

This is a really small detail, but what if we started with KNO3 in the beaker and then mixed in water rather than starting with water in the beaker and then mixing in KNO3? Does the order make a difference?

miznaakbar
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Re: G7 - Homework Problem

Postby miznaakbar » Thu Oct 05, 2017 11:37 pm

From what I understand, the order of mixing a solute and solvent should not matter since the amounts of each should be the same regardless of when they are put in the beaker.

lauren chung 2f
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Re: G7 - Homework Problem

Postby lauren chung 2f » Fri Oct 06, 2017 12:41 am

No, you just need to find the mass of each by calculating 5.45% of 510 g to find the mass of the substance (27.8 g) and then you subtract that from the 510 g to get 482.2 g H2O.


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