# Homework Help: A pH problem

1. Oct 7, 2005

### jena

Hi,

My Question:

Upon evisceration, it was discovered that the frog had died due to acid ingestion. 10mL of gastric juice was found in its stomach required 7.2mL of 0.1 M NaOh for neutralization. Calculate the pH of its gastric juice.

I'm confused, how would I approach this problem.

Thank You

2. Oct 7, 2005

### amcavoy

Well first you might want to find the pH of the NaOH solution. Also, what have you tried?

Alex

3. Oct 7, 2005

### jena

So it would be like this

poH=log[H]
poh=-log[0.1]
poH=1

and

ph+poH=14
ph+1=14
ph=13

Is this correct

thank you

4. Oct 7, 2005

### amcavoy

That looks good for the pH of the NaOH solution. Now, you want to find the pH of the gastric acid. Do you know how to do so from here?

Alex

5. Oct 7, 2005

### jena

No , I still don't know what to do. Also what do I do with the mL's

Thank You

6. Oct 7, 2005

### Staff: Mentor

No need for pOH.

Calculate from simple stoichiometry amount of HCl in the gastric juice, then its concentration - once you know concentration of HCl pH calculation should be a breeze.

7. Oct 8, 2005

### jena

Sorry to reply so late, so I would first find the concentration like so,

M1V1=M2V2

and then use the concentration to find the pH of the acid using this equation

ph=-log(H+)

Is that the correct method?

Thank You

8. Oct 9, 2005

9. Oct 9, 2005

### P-man

Wouldn't it help if you knew the formula of the gastric juice?

10. Oct 10, 2005

### Staff: Mentor

P-man - gastric juice contains mostly HCl.

11. Oct 10, 2005

### P-man

Oh, sorry. I guess that's the stuff in your stomach?