Atomic Mass Help

[eLg]

Can someone tell me how to approach this problem.
I don't need to see any solution. I just want to know the steps in solving this kind of problem.

A 6.01 g sample of copper is contaminated with an additional 0.64g of zinc. Suppose an atomic mass measurement was performed on this sample.

Do I have to create a balanced equation, and convert the values for moles?

[EdEarl]

Sounds like you are on the right track, show some steps toward the solution.

[eLg]

will the balance equation be

 

Cu +Zn -> CuZn?

 

then calculate moles for each elements?then?

[EdEarl]

A 6.01 g sample of copper is contaminated with an additional 0.64g of zinc.

How many grams of Cu in the 6.01 Cu contaminated with Zn?

 

Would Cu combining with Zn to make a Cu and Zn molecule change the number of grams?

[eLg]

I am stuck...

I don't get it...

Help

[EdEarl]

If I have 3 grams of flour and salt in a mixing bowl and 1 gram is salt, how many grams of flour? It isn't a chemistry equation.

[eLg]

2g?

[EdEarl]

Yes, what is the answer for Cu in the mixture of Cu and Zn? Same problem, different numbers, different things. Cu instead of flour, Zn instead of salt.

[eLg]

So I need to subtract the Zn from Cu?

Is the question asking for the atomic mass for Cu only?

[EdEarl]

So I need to subtract the Zn from Cu?

Is the question asking for the atomic mass for Cu only?

No, you need to know how many moles of Cu and how many of Zn.

[eLg]

ok

then after that...

[EdEarl]

We should find out relatively how may atoms of Cu and Zn exist in the sample. If it is 1:1 then Cu+Zn = CuZn, if it is 2:1, then Cu₂Zn, or whatever. Though, I think we can calculate the atomic mass whatever the ratio.

[eLg]

I found the moles of Cu and Zn.Then, I am stuck...

[EdEarl]

How many of each?

[imatfaal]

BTW the question reads "an additional 0.64" - my reading of that wording is that you have a mixture (not a compound) which is 6.01g of Copper and .64 g of Zinc

[EdEarl]

That's right, sorry about that.

[eLg]

I got 0.09457 mol Cu

9.7889*10^-3 mol Zn

 

then?

[EdEarl]

9.457*10^-2 mol Cu

9.789*10^-3 mol Zn

 

10:1 more or less. Kinda like Cu₁₀Zn, you can calculate a better ratio. So the atomic mass would be about 10 (your calculation) Cu atomic masses + 1 Zn atomic mass.

 

If that's wrong, I'm sure Imatfaal will tell us.

[eLg]

I am really confuse now...

[EdEarl]

 

From Wikipedia:

Direct comparison and measurement of the masses of atoms is achieved with mass spectrometry.

 

From Wikipedia:

Similar definitions apply to molecules. One can compute the molecular mass of a compound by adding the atomic masses of its constituent atoms (nuclides). One can compute the molar mass of a compound by adding the relative atomic masses of the elements given in the chemical formula. In both cases the multiplicity of the atoms (the number of times it occurs) must be taken into account, usually by multiplication of each unique mass by its multiplicity.

Copper and Zinc do not form a molecule AFAIK; rather, they combine in a crystal structure. When a sample is measured by a mass spectrometer, it would have about 10 times as many copper as zinc atoms and the measured atomic weight would be either the atomic weight of Cu and atomic weight of Zn or a combination of the two as if they were a molecule. I'm not sure. Imatfaal will know and should tell us. I am also going on the way you were originally trying to solve the problem by balancing a chemical equation, since you were in lecture, not me, I'm assuming you know something about what your instructor wants.

[eLg]

He did not say anything. He briefly describe the topic then ask us to this.

[EdEarl]

The atomic mass as I suggested would be the average for that crystal, imo.

[eLg]

I got the answer thank you...

[EdEarl]

yw