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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: mrummel on April 15, 2012, 09:46:25 PM

Title: Saturated Solutions
Post by: mrummel on April 15, 2012, 09:46:25 PM
Hey everybody, I have a test tomorrow on saturated solutions, Ksp, Qsp and related stuff. There's a problem on the study guide that I'm having quite a bit of trouble with and need help. Any help would be appreciated, thanks

The Problem

In a saturated solution of silver carbonate the concentration of [Ag+] = 1.86x10-4M

A) Calculate the concentration of the carbonate ion, CO32- in this solution





B)Determine the Ksp of silver carbonate




C) Silver carbonate is allowed to reach equilibrium in a solution that contains 1.33 x 10-3M AgNO3

i. Using Lechatelier's Principle (arrows), show the effect that the silver nitrate has on the solubility of silver carbonate

ii. Calculate the solubility of silver carbonate in this solution
Title: Re: Saturated Solutions
Post by: UG on April 15, 2012, 10:03:01 PM
Quote from: mrummel on April 15, 2012, 09:46:25 PM
A) Calculate the concentration of the carbonate ion, CO32- in this solution
Can you write a balanced equation for the dissolution/dissolving of silver carbonate in water?
Title: Re: Saturated Solutions
Post by: mrummel on April 15, 2012, 10:07:43 PM
Quote from: UG on April 15, 2012, 10:03:01 PM
Quote from: mrummel on April 15, 2012, 09:46:25 PM
A) Calculate the concentration of the carbonate ion, CO32- in this solution
Can you write a balanced equation for the dissolution/dissolving of silver carbonate in water?

Yes, I'm pretty sure it would be Ag2CO3 ::equil:: 2Ag+ + CO32-
Title: Re: Saturated Solutions
Post by: UG on April 15, 2012, 10:10:47 PM
Ok good, so if you know the concentration of silver ions in the saturated solution, going from your equation then the concentration of CO32- is?
Title: Re: Saturated Solutions
Post by: mrummel on April 15, 2012, 10:13:18 PM
Quote from: UG on April 15, 2012, 10:10:47 PM
Ok good, so if you know the concentration of silver ions in the saturated solution, going from your equation then the concentration of CO32- is?

Would it be 3.72x10-4? Or do you square it? My teacher went over this really fast and I couldn't figure out how to do it.
Title: Re: Saturated Solutions
Post by: UG on April 15, 2012, 10:18:18 PM
The concentration of CO32- should be half that of the silver ions. Look at your equation again.
Title: Re: Saturated Solutions
Post by: mrummel on April 15, 2012, 10:20:10 PM
Quote from: UG on April 15, 2012, 10:18:18 PM
The concentration of CO32- should be half that of the silver ions. Look at your equation again.

Oh... Now I feel kind of stupid.

So the concentration is 9.3x10-5
Title: Re: Saturated Solutions
Post by: UG on April 15, 2012, 10:28:49 PM
Yes ok good, now for B, do you know how to write the Ksp equation? It is like any equilibrium type equation, use your chemical equation to help if needed.
Title: Re: Saturated Solutions
Post by: mrummel on April 15, 2012, 10:32:55 PM
Quote from: UG on April 15, 2012, 10:28:49 PM
Yes ok good, now for B, do you know how to write the Ksp equation? It is like any equilibrium type equation, use your chemical equation to help if needed.

Yeah I have B, but C ii I don't know how to do. I've written this equation for C i.

AgCO3  ::equil:: 2Ag+ + CO32-

AgCO3 goes up, 2 Ag+ initially goes up, then down, and  CO32- goes down. But how do I do ii?
Title: Re: Saturated Solutions
Post by: UG on April 15, 2012, 10:53:50 PM
A good approximation you can make here is that the value of [Ag+] in your Ksp equation is equal to 1.33 x 10-3, you can then work out the concentration of CO32- and this will be the solubility of silver carbonate in 1.33 x 10-3M AgNO3