Question

Find the pH of the following solutions:
a) 0.0005 mol/L H2SO4
b) 0.00005 mol/L Ba(OH)2

Answer 1

When the \(\large H_2SO_4\) concentration is 0.0005 mol/L,
what is the \(\large[H^+]\) concentration?

Answer 2

@thomaster I already did both but want to check my answer please :)

Answer 3

well then post your answers so I can check them

Answer 4

Ok I got a) as 3 and b) as 4 is that correct?

Answer 5

\(\Large pH=-log[H^+]\)

for A, the \(\large[H^+]\) = 0.0010 mol/L (since there are 2 Hydrogen atoms in H2SO4.

\(\large pH=-log[0.0010]=3\) So that one is correct \(\LARGE\ddot\smile\)

Answer 6

Alright :)

Answer 7

Oke,.. the page just crashed xD
Let me type B again

Answer 8

Uhuh I can wait, don't worry :)

Answer 9

pff again... I think somethings wrong with OS...
I'll do it in steps before I lose it again

Answer 10

Cool :D

Answer 11

It isn't crashing for me though...

Answer 12

For B we don't have the H+ concentration, but the OH-
This \([OH^-]\) concentration is 0.00010 (since there are 2x OH- in Ba(OH)2)

Answer 13

With the OH-, we can't calculate the pH directly. So we need to calculate pOH first.
\(\Large pOH=-log[OH^-]\)

Answer 14

\(\Large pOH=-log[0.00010]=4\)

Answer 15

So the pOH = 4
Now look at this image:

Answer 16

To go from pOH to pH, you need to use:
\(\LARGE pH=14-pOH\)

Answer 17

Because pH + pOH = 14

Answer 18

So what is the pH for B?

Answer 19

But aren't we meant to use pOH = -log (OH)- here?

Answer 20

Is the pH 10 then?

Answer 21

@thomaster

Answer 22

I used pOH = -log[OH-] here:) didn't you see?
And yes the pH = 10

Answer 23

That would mean before I got the pOH then I didn't read the question properly :/ thanks so much for explaining @thomaster

Answer 24

No problem :)