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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: Zoloft on February 08, 2009, 06:45:58 PM

Title: Arrrrr very basic problem, yet confused.
Post by: Zoloft on February 08, 2009, 06:45:58 PM
According to one of my labs, the atomic mass of Zinc can be determined by the balanced equation,

Zn + 2HCl ---> H2 + ZnCl2

Then it says "the number of moles of zinc metal that reacted be be calculated"

So then I use the number of moles of H2 that I calculated (we did a barometric experiment and calculated moles of H2,n, from n = PV/RT) and I do:

.00581 mol H2 x (1 mol Zn / 1 mol H2) = .00581 mol of Zn

then it says "Since all the original Zinc is consumed in this reaction, the atomic mass of zinc can thereby be determined..."

My question is, how do I determine this?
Title: Re: Arrrrr very basic problem, yet confused.
Post by: Borek on February 08, 2009, 07:11:57 PM
I suppose you know mass of zinc used?
Title: Re: Arrrrr very basic problem, yet confused.
Post by: Zoloft on February 08, 2009, 07:20:59 PM
Quote from: Borek on February 08, 2009, 07:11:57 PM
I suppose you know mass of zinc used?
Yes, it was .587 grams.

Obviously the Atomic mass is 65.41 g, but how do I determine this (or a number close to this) using the experimental procedure?
Title: Re: Arrrrr very basic problem, yet confused.
Post by: nj_bartel on February 08, 2009, 08:03:40 PM
MWZinc = x gramsZinc / 1 moleZinc

grams / moles
Title: Re: Arrrrr very basic problem, yet confused.
Post by: Zoloft on February 08, 2009, 08:14:40 PM
Quote from: nj_bartel on February 08, 2009, 08:03:40 PM
MWZinc = x gramsZinc / 1 moleZinc

grams / moles

Hmmm, so in this case the number of moles of Zinc is the moles of Zinc using the stoichiometric relationship, right?

Title: Re: Arrrrr very basic problem, yet confused.
Post by: Borek on February 09, 2009, 02:51:17 AM
Try to devise a scenario in which it is not.