how to find log and antilog in acid and bases concept.

[sony_pabla4043]

i am really confused and cant understand whether real mcat test will provide log tables for calculations.
And i want to know that how to calculate -log[H3O+]=4.4.

[nathan.blu4013]

easy! basically you just need to know how to approximate.

Here is the idea, typically the concentration of the H30+ (I'll call them H+ since that's typically what you see) is 10^X (that's: ten to the power of X). So:

-log(10^X) always equals X, since it is a log base 10.

definition of log is here: http://en.wikipedia.org/wiki/Logarithm

....another important one to know is how to approximate a log of something like 4.2938x10^-29

here is how you do it.

-log(4.2938x10^-29) = -(log(4.2938) + log(10^-29))

= 29 - log(4.2938)

since you are using the log scale, small increases (like 4.2938) will have a small log...so your answer is essentially about 28. I think that's as much as you need to know...anyone else?

[admin]

The real MCAT is not interested in log/antilog tables. They want to test your reasoning/logic skills feeling that is the way to determine if you would have clinical skills one day.

-log[H+] = 4.4

log[H+] = -4.4

both sides can be raised to the power of 10 (you must know the rules of logarithms, you can look at the link provided by nathan.blu4013 or use the review in The Gold Standard MCAT book):

[H+] = 10^-4.4

Since it is a multiple choice exam, check the answers and you should find one answer between 0.0001 and 0.00001.