# Need help w/ concentration, absorbance, etc.

Hello, and thanks for any help I recieve ahead of time:

So, the question/requirement reads:

"Since you now know the concentration and volume, determine the number of grams of copper in the unknown solution."

Since the absorbance of the unknown sample was given (0.365), I came up with a graph (concentration on the x axis and absorbance on the y), its line-of-best fit and it's relevant equation (y=2.27625x+0.0631).

After using (x,y) which (I'm hoping I did this right), is equivalent to (concentration, absorbance), I inserted (concentration, 0.365) into the equation for the line of best fit, y=2.27625x+0.0631. For an x/concentration value of (concentration, 0.365), I got 0.13263.

If I am on the right path, which I am starting to severely doubt I am, I just do not know where to go next in the process to get mols or anything to get me on the way to being able to get the number of grams of copper in the 'unknown sample'.

So far the values/givens I know for sure are:

*Absorbance, Unknown Sample:0.365

*Equation of the line of best fit, Absorbance v. Concentration: y=2.27625x+0.0631

*(given):grams of brass used to make unknown solution: .9677 g

*(calculated) Concentration of the Unknown Sample: 0.13263

---------Again, any help on this particular question would be greatly apprecieated. We have not even began to touch on molarity this year, and I believe (as does the rest of my last-regular chemistry class I had last year, who I still keep in touch with) that we spent approximately 1 day on this last year.

Again, thank you in advance:

-Drano365

If the molarity of the Cu2+ions = 0.13263, then you will have 0.13263 moles Cu2+ per litre. The number of moles of Cu2+ in your sample = volume of solution in L x molarity. If atomic mass of copper = 63.546, then each mole of Cu or each mole of Cu2+ will have a mass of 63.546g