I am completing my lab and cannot figure this out. I need someone to go over it and make sure I am right because I can't figure out why my empirical formula does not match the molecular formula. #7 is the one I am really having a problem with, but here is all the info so you can see if I made an error.

Question

Here are my measurements and calculations. (They were given to us by the teacher, so I did not actually measure them).
Mass of empty beaker 55.45g
mass of zinc metal 1.80 g
mass of beaker containing zinc chloride 58.16

1.)Calculate the mass of zinc chloride produced:
58.16g-55.45g= 2.71 g

2.)Calculate the mass of chlorine reacted:
2.71 g ZnCl2 - 1.80 g Zn= 0.91 g Cl

3)Calculate moles of zinc based on original mass of Zn:
1.80 g Zn x 1 mole/ 65.39 g Zn = 0.0275 mole Zn used

4) Calculate moles of chlorine reacted based on your answer for #2
0.91 g Cl x 1 mole/35.45 g Cl = 0.0257 moles of Cl used

5) What is the experimental empirical formula of zinc chloride?
Determine the simplest whole number ratio of moles of zinc used,
to moles of chlorine reacted in the zinc chloride that was produced. (Take your answers to #4 and #5, and divide both values by whatever value is smaller.)
Cl=0.0257/0.0257 =1 Zn= 0.0275/0.0257 = 1.07 = 1 so a 1:1 ratio

6) Determine the actual empirical formula of zinc chloride, based on the ionic charges of zinc and chloride ions, using your rules for ionic nomenclature
ZnCl2
7) Does your experimental empirical formula (answer to #5) agree
with the known empirical formula (answer to #6) of zinc chloride? List and describe some sources of error that may have affected your results.

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Any help would be appreciated. I have racked my brain over this for 2 hours and cannot figure it out. Thanks.

Answer 1

I don't see anything wrong with your calculations, although I don't know exactly how the experiment was to be conducted. It would appear to me that since your teacher gave you a made up experiment with numbers that s/he gave you bad data OR the numbers were made up wrong on purpose. Since I don't know the particulars of the experiment I can't give any hints as to what may have gone wrong. That may be the exercise; i.e., for you to go through the experiment (I assume you know the details of the experiment) and determine how an error may have been made.

Answer 2

Thank you :)