# A2 AQA Confusing find pH question

#1
0
6 years ago
#2
(Original post by koolgurl14)
When water is added, does the solution become stronger or weaker?
0
6 years ago
#3
First calculate the moles of Hcl= 0.154*10/1000=1.54x10-3
then calculate the new concentration of Hcl after adding water= 1.54x10-3/(990+10)*1000=1.54x10-3
then caluclate pH= -log(1.54x10-3)=2.81
1
#4
(Original post by ghostmarston)
First calculate the moles of Hcl= 0.154*10/1000=1.54x10-3
then calculate the new concentration of Hcl after adding water= 1.54x10-3/(990+10)*1000=1.54x10-3
then caluclate pH= -log(1.54x10-3)=2.81
dividing with 0.1 deffo wont give u the same number?
0
#5
(Original post by KaylaB)
When water is added, does the solution become stronger or weaker?
Weaker?
0
6 years ago
#6
where did you get 0.1 from?
1
6 years ago
#7
(Original post by KaylaB)
When water is added, does the solution become stronger or weaker?
I know what you mean but that question doesn't make much sense.
0
6 years ago
#8
(Original post by koolgurl14)
Weaker?
Exactly, as the answers has been posted above, just remember that the general way to do these questions is to calculate the amount of moles of the acid in the beginning, then calculate the concentration of the acid for the total volume, then find the pH as you would normally
1
6 years ago
#9
(Original post by B_9710)
I know what you mean but that question doesn't make much sense.
Care to elaborate?
0
6 years ago
#10
You know the concentration of H+ in water at 298k is around , using n=cv you can work out the moles of H+ in the water.
Then you want to work out the moles of H+ added to the solution.
Then use pH.
0
6 years ago
#11
(Original post by KaylaB)
Care to elaborate?
Well depending on what you add to a solution, the solution could get more strongly acidic, more strongly alkaline, or more weakly acidic or alkaline.
0
6 years ago
#12
(Original post by B_9710)
Well depending on what you add to a solution, the solution could get more strongly acidic, more strongly alkaline, or more weakly acidic or alkaline.
I said about adding water a neutral substance, which can be used for dilution
0
6 years ago
#13
Use the formula :

H+ new =[H+] old x Old Volume / New Volume
0
6 years ago
#14
(Original post by KaylaB)
I said about adding water a neutral substance, which can be used for dilution
That's not what the question said though. But yeah cool I'm not saying your wrong though.
0
6 years ago
#15
(Original post by B_9710)
That's not what the question said though. But yeah cool I'm not saying your wrong though.
It literally says in the question that the HCl is added to 990cm^3 of water
0
6 years ago
#16
(Original post by KaylaB)
It literally says in the question that the HCl is added to 990cm^3 of water
So does adding acid to water make the solution stronger?
0
6 years ago
#17
(Original post by B_9710)
So does adding acid to water make the solution stronger?
Well there isn't really a concentration of water, so adding some acid to water would still just make a dilute acid
0
6 years ago
#18
(Original post by KaylaB)
Well there isn't really a concentration of water, so adding some acid to water would still just make a dilute acid
Yeah I know, this is why what you said doesn't make much sense, the acid gets more dilute, but you can't say it gets weaker. pH does not really tell you how strong an acid is unless you're comparing 2 acids with same conc.
0
6 years ago
#19
(Original post by B_9710)
Yeah I know, this is why what you said doesn't make much sense, the acid gets more dilute, but you can't say it gets weaker. pH does not really tell you how strong an acid is unless you're comparing 2 acids with same conc.
Ah okay so it was just my wording was a bit off, thanks for letting me know so I can stop sounding like a fool
0
6 years ago
#20
(Original post by KaylaB)
Ah okay so it was just my wording was a bit off, thanks for letting me know so I can stop sounding like a fool
I'm not trying to say you're a fool or anything like that or come across as a knob, just being pedantic.
0
X

new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### Poll

Join the discussion

#### How did your AQA A-level Psychology Paper 1 go?

Loved the paper - Feeling positive (230)
41.82%
The paper was reasonable (234)
42.55%
Not feeling great about that exam... (51)
9.27%
It was TERRIBLE (35)
6.36%