Buffer pH help?
I have to be missing something here, something obvious, but I just don't understand what's going on here.
200Cm3 of 3.2 mol dm-3 HCOOH,
800Cm3 of 0.5 mol dm-3 NaOH
Buffer volume = 1dm3
Ka is 1.4*10-4
The conc. of H+ is Ka*HA/A isn't it?
But the values given already are concentrations and it can't be to do with "total volume" because it's 1.
The markscheme values in the calculation are 0.4 for NaOH, (isn't that the no. of moles??? Conc*volume?),
and 0.24 for HCOOH... where on Earth is that value even coming from?
200Cm3 of 3.2 mol dm-3 HCOOH,
800Cm3 of 0.5 mol dm-3 NaOH
Buffer volume = 1dm3
Ka is 1.4*10-4
The conc. of H+ is Ka*HA/A isn't it?
But the values given already are concentrations and it can't be to do with "total volume" because it's 1.
The markscheme values in the calculation are 0.4 for NaOH, (isn't that the no. of moles??? Conc*volume?),
and 0.24 for HCOOH... where on Earth is that value even coming from?
Original post by Pigster
How many mol of HCOOH do you start with?
How many mol of NaOH are you adding?
How many mol of HCOOH will be left after neutralising some of them?
How many mol of HCOO- will be formed in this partial neutralisation?
How many mol of NaOH are you adding?
How many mol of HCOOH will be left after neutralising some of them?
How many mol of HCOO- will be formed in this partial neutralisation?
EDIT - OH! I see what you're saying, so you subtract the moles value of NaOH from HCOOH's or something. I've never needed to do that before which is why I didn't get it, but that's quite simple then. Thanks!
(edited 8 years ago)
I just calculated it all and got a pH of 3.99 or 4.00 I am not great at this and just practicing too so can you tell me if this is right?
(edited 8 years ago)
Original post by Hexaneandheels
I just calculated it all and got a pH of 3.99 or 4.00 I am not great at this and just practicing too so can you tell me if this is right?
3.99 is correct!
Posted from TSR Mobile
Yay!
Original post by Jimmy20002012
Original post by Jimmy20002012
Yep
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