Acids and bases 3

?
Example Q:

0.005 moles of NaOH added to .05L of buffer solution (which itself is .24M of NH3 and .2M of NH4Cl. Initial pH = 9.25.
What is the resulting pH?
You could find the [] of NaOH with moles/ ?..
0.005/0.5 = 0.01M

Things to clock: NaOH looks like a strong base, NH4Cl looks like an acid component.
1 of 6
The fact that NaOH is a strong base tells you that:

The fact that NH4Cl is an acid component tells you that:
- the changes in the RICE table will be equal to the number of OH- that appear.

- the OH- will react with dissociated NH4 bit.

So what you got RICE-wise?
2 of 6
...
R. NH4+ + OH- -> H2O + NH3
I. 0.2 0.01 0.24
C. -0.01 -0.01. +0.01
E. 0.19 0 0.25
3 of 6
What do you do with that?
pH = initial pH + log (final acid component / initial acid component), so...

9.25 + log (0.25/0.19)
9.37

Conclusion: buffer is pretty decent.
4 of 6
Another example:

0.03 moles of HCl is added to 0.5L of a buffer solution, which itself is 0.24M of NH3 and 0.2M of NH4Cl. Initial pH = 9.25.
What’s the resulting pH?
First you deduce the [] of the HCl, so moles over L:
0.03 / 0.5 = 0.06

What will the RICE table look like?
5 of 6
...
R. NH3+ + H3O+ -> H2O + NH4+
I. 0.24 0.06 0.2
C. -0.06 -0.06 +0.06
E. 0.18 0 0.26
6 of 6

Other cards in this set

Card 2

Front

The fact that NaOH is a strong base tells you that:

The fact that NH4Cl is an acid component tells you that:

Back

- the changes in the RICE table will be equal to the number of OH- that appear.

- the OH- will react with dissociated NH4 bit.

So what you got RICE-wise?

Card 3

Front

...

Back

Preview of the front of card 3

Card 4

Front

What do you do with that?

Back

Preview of the front of card 4

Card 5

Front

Another example:

0.03 moles of HCl is added to 0.5L of a buffer solution, which itself is 0.24M of NH3 and 0.2M of NH4Cl. Initial pH = 9.25.
What’s the resulting pH?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all Acids, bases and salts resources »