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Please look at the given formula. Copy it down. Note that [H+] is given and is 4.3*10^(-14).
Just substitute this VALUE for [H+] into the formula, calculate the log, and then put a negative sign in front of it.
so pH = -log4.3*10^(-14)
then pH=-log4.3-log10^(-14) ?
Enclose the argument (4.3 ....) in parentheses. Otherwise you're doing fine. You'll need to evaluate that log. Then, you'll need to negate the value of the log (put a - sign in front of it).
I'm stuck on evaluating the log -log4.3
I know -log10^(-14) is just (-14)
You have too many - signs in your expression. Only one of them belongs there. CAn you fix this? As before, evaluate log (..... ) before writing the neg. sign in front of it.
[H+] is given and is 4.3*10^(-14). 4.3 * 10^(-14) is a product. What is the product rule for logs? True, log 10^(-14) is -14.
logbAC = logbA + logbC
Yes, that's correct. So, whats the log of the product 4.3 * 10^(-14) ?
ehh, i'm stumped
What's the log of 4.3? What's the log of 10^(-14)? Whats the log of the product of those two quantities?
oh wait is it -0.63347?
I was hoping you'd evaluate the 2 logs and then add the results together before brining in that negative sign. You have already told me, correctly, that log 10^(-14) is -14. What is the log of 4.3?
the log of 4.3 is 0.63347 right?
Yes, that looks good. Now, add to gether that 0.63347 and that -14. Can you explain why this is necessary?
Note that one is positive and the other negative.
would you solve it like log0.63347 * -14
No, you no longer need that "log" operator, because you've already found the logs of 4.3 and 10^(-14).
ohh okay so it's just 0.63347 * -10?
This isn't multiplication, so throw out that *. Combine (do not multiply) 0.63347 and -14.
* means multiplication + denotes addition
I got -9.366..
oh wait careless mistake, now my answer is -13.366..
much better. Now negate that result (multiply it by -1). \
it is it's reciprocal, 13.3?
No. You have -13.366, which is a negative number, and need only multiply that negative number by -1. what is the result of that? It's true that an EXPONENT of -1 indicates reciprocal in some cases, but not in this one.
the result of -13.366 * -1 is 13.366?
right, and that's to 3 decimal places. How many decimal places were called for?
it rounds to 13.4 right?
Right. That's rounded off to the nearest 10th. Your answer? "The approximate pH is ... ?"
The appoximate pH is 13.4
Right. Very good. Any questins about this procedure?
Not anymore, thank you so much for your help!
You're welcome. Best of luck to you, and M. C. Bye!