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Good assumption on pH or not?

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PJB:
Hi all,
 Here is the question:  "If you add 0.82 g of NaCH3CO2 to 100mL of a 0.10 M CH3CO2H solution, what is the new pH of the resulting solution?  For CH3CO2H Ka=1.8x10^-5.

The answer options are A. 1.73 B. 2.4 C. 3.2 D. 4.74 and E. 5.74  Am I correct in thinking that since -log1.8x10^-5 is 4.74, then the answer must be E. 5.74 since adding a base alwasy raises pH?

I realize that this is not the ideal way to work this, but I am just trying to apply some common sense to my efforts instead of just rambling through the calculations.  I am an absolute algebra mess.  I can get A's on all my open book/open note quizzes, but I got a C- on my first exam.  I feel like I look at a problem on an exam and have no clue, it is all just a mess of mumbojumbo so I am trying to step back and relax and think more logically/analytically about the problem as a whole.  Wish me luck and any suggestions for my math challenged mind would be appreciated!
Pam

Grumples:
I'd wager you're right, although if you got a problem like that on a test, I would recommend checking it anyway with the equation pH = pKa+log(base/acid).  

Borek:

--- Quote from: PJB on May 30, 2005, 03:40:02 PM ---The answer options are A. 1.73 B. 2.4 C. 3.2 D. 4.74 and E. 5.74  Am I correct in thinking that since -log1.8x10^-5 is 4.74, then the answer must be E. 5.74 since adding a base alwasy raises pH?
--- End quote ---

Always rises, but you don't know what was the starting value - 2.88 in this case. Everything above is possible. You must check amount of sodium acetate added and use Handerson-Hasselbach equation (the one posted by Grumples).

Check out BATE - while it can't be used on the exam, it can be usefull in other situations.

PJB:
Thanks!  That was helpful, you guys are my professors for this class whether you want to be or not!  :) but  could you tell me what BATE is all about please?  
Pam

Borek:
Check my website (links in signature).

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