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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Redbox32 on March 13, 2012, 06:45:02 AM

Title: What are the concentration of the three solutions?
Post by: Redbox32 on March 13, 2012, 06:45:02 AM

If the concentration of the issued (standard) CuSO4 solution is 1.80 * 10^-2 M, what are the concentrations of each of the three solutions prepared for the calibration curve.

First flask = 0mL of Cu^2+ solution and 10ml of 2M NH3
Second Flask = 5mL of Cu^2+ solution and 10ml of 2M NH3
Third Flask = 15mL of Cu^2+ solution and 10ml of 2M NH3

Title: Re: What are the concentration of the three solutions?
Post by: Arkcon on March 13, 2012, 06:52:34 AM

Can you begin to solve this one for yourself?  That is part of the Forum Rules, posted in Red, at the top of every page of this forum.  What is a calibration curve?  What is it supposed to do?  Can you tells us, for starters, how much Cu is in the first flask?

Title: Re: What are the concentration of the three solutions?
Post by: Redbox32 on March 14, 2012, 04:22:36 AM

Hi, Sorry i didn't realise that this was the site rules.
I think imay have an idea but i'm not totally sure.

First flask i work out the concentration to be 2M because you were only adding in the 2M NH3 solution.
Second Flask and third flask: I used this equation. (n(NH3)-n(Cu^2+))/V(NH3+Cu^2+)
Is this method correct?

Title: Re: What are the concentration of the three solutions?
Post by: Borek on March 14, 2012, 05:40:47 AM

Quote from: Redbox32 on March 14, 2012, 04:22:36 AM

First flask i work out the concentration to be 2M

2M of what? You have copper sulfate and ammonia in the solution, each will have a different concentration. You have to treat their concentrations separately.

Title: Re: What are the concentration of the three solutions?
Post by: AWK on March 14, 2012, 06:18:30 AM

For solutions 2 and 3 recalculate concentration of both reagent to the final volume, then calculate stoichiometry of complex formation