# Homework Help: Find the [H3O+], [OH‐], pH, and pOH

1. Jul 4, 2012

### IntegrateMe

A solution is prepared to be 0.1475 M in Sr(OH)2. Find the [H3O+], [OH‐], pH, and pOH.

I'm not quite sure where to go from here. I was thinking I can start by writing out the net ionic equation:

Sr(OH)2 → Sr2+ + 2OH-

But I don't really know how that helps me. Any insights?

2. Jul 4, 2012

### Saitama

Find the concentration of OH-.

3. Jul 4, 2012

### IntegrateMe

The book shows that the concentration of OH is 2(.1475M), but I'm not sure how that was obtained. I understand that there are 2 hydroxide ions, but why do we use the moles of the solution?

4. Jul 4, 2012

### IntegrateMe

Seriously, why can't ANYBODY help me? I figured the problem was relatively easy, am I asking in the wrong way?

5. Jul 5, 2012

### Staff: Mentor

Geez, you didn't get an answer in two hours, on the Independence Day evening, and you are already frustrated? Get some pills for patience.

Seeing how you don't know what to do makes me wonder you are missing... What is the definition of the concentration? If you have 1L of the 0.1475 M solution, how many of Sr(OH)2 are there? Look at the dissociation equation - how many moles of OH- are there?

6. Jul 5, 2012

### Staff: Mentor

Geez, you didn't get an answer in two hours, on the Independence Day evening, and you are already frustrated? Get some pills for patience.

Seeing how you don't know what to do makes me wonder you are missing... What is the definition of the concentration? If you have 1L of the 0.1475 M solution, how many moles of Sr(OH)2 are there? Look at the dissociation equation - how many moles of OH- are there?

7. Jul 5, 2012

### IntegrateMe

There are 2 moles of OH- in Sr(OH)2.

Why do we multiple this 0.1475 M solution by the number of moles of one part of the reaction, though?

8. Jul 5, 2012

### Staff: Mentor

What is the definition of the concentration?