Tuesday, May 17, 2011

Final Exam Review

15)  Give chemical formulas for the following compounds:


a.  cobalt (II) acetate:
CO(C2H3O2)2


b.  hydronitric acid:
H3N
c.  aluminum dichromate:
Al2(Cr2O7)3


d.  dinitrogen pentoxide:
N2O5


e.  cesium carbonate:
Cs2CO3


f.  magnesium chlorate:
Mg(ClO3)2


g.  lead (II) nitride:
Pb3N2


h.  acetic acid:
HCH3COO






31)  Think of a topic or question you think should have been covered


Like many, I had trouble with sig figs when working with pH and pOH, so I thought more clarification would be helpful.


pH=-log(H)
(H: morality)


#total sig figs morality= # sig figs AFTER decimal for pH and pOH




example:


pH=-log(.0228)
     = 1.642


-.0228 has 3 sig figs allowing the answer to have 3 sig figs AFTER the decimal


*the concept is applied to the reverse as well


H=10^-pH
   = 10^-4.82
   =1.5 x 10^-5 M


-The pH only has 2 sig figs AFTER the decimal => the molarity has a TOTAL of 2 sig figs


*The same rules apply to pOH

4 comments:

  1. I disagree with a, b, c, d, and h (although you were on the right track every time).
    a. The metal should always come first in the equation, and the two should be after acetate.
    b. It should be H3N
    c. Dichromate is Cr2O7
    h. The H+ ion should come before the acetate - that's just the standard way of writing it.

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  2. good job katherine!!!To make your blog more functional you could have used math type, also while your 31 was really helpful and it gave useful information, but it was part of another question on the review.

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  3. hi! Also, i thing you typed "morality" instead of "molarity".I thing that you explained the sig fig issue with pH and molarity will. It clarified the confusion I have been having. Good Job!

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  4. Katherine you did a great job on your blog! It is very organized and neat, which makes it easy to follow. The only thing I would suggest is that when you were writing your chemical formuals you should have explained how you came to them, showing that you added the two ions together, swapping their charges and if needed reducing the charges. Over all you did a great job and I espeically liked how you included a question abou sig figs with pH and pOH.

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