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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: chinookkola on April 21, 2015, 05:29:27 PM

Title: Solubility Problems... Precipitates
Post by: chinookkola on April 21, 2015, 05:29:27 PM

I have a grade 11 chemistry assignment and I am stumped on this one question. I can't find it anywhere else on the web, or something like it.

At 100°C, 200g KNO3 and 15g NaCl are added to 100mL water. The solution is kept at the same temperature until only 40mL of water remains. What is the mass of each solid precipitate?

I changed the numbers because I am not looking for only the answer, but I want to learn how to do this.

Can someone help?
Thanks  ;D

Title: Re: Solubility Problems... Precipitates
Post by: Hunter2 on April 22, 2015, 06:12:11 AM

The mass of the salts is not changing. It will be still 200 g potassium nitrate and sodium chloride.

Title: Re: Solubility Problems... Precipitates
Post by: Borek on April 22, 2015, 09:55:23 AM

Quote from: Hunter2 on April 22, 2015, 06:12:11 AM

The mass of the salts is not changing. It will be still 200 g potassium nitrate and sodium chloride.

Question asks for mass of precipitates, not for the general amount of salts.

I must say I have no idea how to approach it. I bet there is something wrong with the way question is formulated, it won't be easy even on graduate level and can't be solved without experimental data.

Title: Re: Solubility Problems... Precipitates
Post by: Hunter2 on April 22, 2015, 02:43:29 PM

Yes you are right, it was my mistake to overlook the word precipitate. The only approach what I can think is to check the soloubilty of potassium nitrate and sodium chloride and also of potassium chloride and sodium nitrate.