# Homework Help: PH question, I really don't get this!

1. Dec 5, 2006

### night nurse 991

1. The problem statement, all variables and given/known data
What is the [H3O+] of acid rain with a pH of 4.23?

2. Relevant equations
pH = -log[H30+]
pOH = -log[OH-]
pH + pOH = 14

3. The attempt at a solution

the four possible choices are
a. 1.7 x 10^-10
b. 5.8 x 10^-5
c. 2.3 x 10^-4
d. 1.7 x 10^5

2. Dec 5, 2006

You are given the pH and need to calculate the concentration of the $$H_{3}O^+$$ ions. Which equation should you use?

3. Dec 5, 2006

### night nurse 991

I know I have to use the first one but I don't know how to do the reverse of it

4. Dec 5, 2006

### Noobcake

Since pH = -log[H30+] or pH = -log[H+]
H3O+/H+ = 10^(-pH)

Last edited: Dec 5, 2006
5. Dec 5, 2006

### night nurse 991

But I dont get how to plug it in on my calculator

6. Dec 6, 2006

### Noobcake

10^(-pH)
10 to the -pH power.

7. Dec 6, 2006

### night nurse 991

Oh okay I got the answer thank you so much!