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.
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.
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.
Thank you :)
Well, it seems like you've done a great job with your calculations! However, it does appear that your experimental empirical formula (1:1 ratio) does not match the known empirical formula of zinc chloride (ZnCl2).
Now, there could be a few sources of error that might have affected your results. Here are a couple of possibilities:
1. Measurement errors: Even though the measurements were given to you by your teacher, there could still be some slight errors in the values. These small inaccuracies can accumulate and affect the final result.
2. Contamination: It's possible that some impurities or contaminants in the zinc sample or in the beaker could have affected your calculations and led to a different empirical formula.
3. Human error: As clever as we humans are, we are not immune to making mistakes. It's always possible that a small error in one of your calculations or steps led to a discrepancy between your experimental and known empirical formulas.
Remember, science can be a bit tricky sometimes, and even the best of us can get stuck. Keep your spirits high and try again!
From your calculations, it seems like you have correctly determined the empirical formula of zinc chloride to be ZnCl2. However, you mentioned that the empirical formula does not match the molecular formula, which suggests that there might be a discrepancy.
To determine whether the experimental empirical formula matches the known empirical formula, we compare them. In this case, the experimental empirical formula is ZnCl2, and the known empirical formula is also ZnCl2. Therefore, they do agree, and your experimental results match the known empirical formula.
Regarding the potential sources of error that may have affected your results, there are a few possibilities to consider:
1. Measurement errors: Even though the measurements were given to you by the teacher, there is always the possibility of slight inaccuracies or inconsistencies in the measurements.
2. Sample purity: The presence of impurities in the zinc metal or other reactants could affect the accuracy of your results. For example, if the zinc metal contained impurities, it could affect the stoichiometry of the reaction.
3. Experimental procedure: Mistakes in carrying out the procedure or transferring substances between containers could introduce errors in the measurements and calculations.
4. Assumptions: The assumptions made during the calculations, such as assuming complete reaction and neglecting any other possible reactions or side products, could contribute to differences between the experimental and known empirical formulas.
It's important to keep in mind that laboratory experiments can be subjected to various sources of error, and it's crucial to critically evaluate your results and consider potential sources of discrepancy.