- #1

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The problem:

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Students at Eastern Illinois University intended to prepare copper(II) carbonate by adding a solution of CuSO

_{4}* 5 H

_{2}O to a solution of Na

_{2}CO

_{3}.

CuSO

_{4}* 5 H

_{2}O(aq) + NaCO

_{3}(aq) ----> CuCO

_{3}(s) + Na

_{2}SO

_{4}(aq) + 5 H

_{2}O(l)

After warming the mixture to 60 degree C, the gelantinous blue precipitate coagulated into an easily filterable pale green solid. The product was filtered, washed, and dried at 70 degree C. Copper in the product was measured by heating .4g of solid in a stream of methane at high temerpature to reduce the solid to pure Cu, which is weighed.

4 CuCO

_{3}(s) + CH

_{4}(g) --heat--> 4 Cu(s) + 5 CO

_{2}(g) + 2 H

_{2}O(l)

In 1995, 43 students found a mean value of 55.6 wt% Cu with a standard deviation of 2.7 wt%. In 1996, 39 students found 55.9 wt% with a standard deviation of 3.8 wt%. The instructor tried the experiment 9 times and measured 55.8% with a standard deviation of 0.5 wt%. Was the product of the reaction probably CuCO

_{3}? Could it have been a hydrate, CuCO

_{3}* xH

_{2}O?

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First since there are many different data sets, so I thought it was probably a comparison of t values for the 3 data sets. The equation is t= [ |x

_{mean1}-x

_{mean2}| / s ]* sqrt(n

_{1}n

_{2}/n

_{1}+n

_{2}). and it seems like there was values to plug into each to them, but then I realized the question was not asking for a comparison of values, but to determine what the product was.

I looked through the sections in the textbook that we went over in class, but none of them expained how to do this or showed any similar examples. So can anyone help?

Even if you don't know the answer or aren't certain of how to solve this problem, can you at least explain how you

*might possibly*sovle/start this problem yourselves? (it might give me ideas)

Thanks