if its weak
YOU MUST USE KA .. YOU CANNOT GET AROUND THAT.
You can. Using the method Shinny used above. Due to incomplete ionisation of weak acids in water, you can always assume the pH is greater than that for complete ionisation (but not greater than 7).
It is not always useful to perform a full calculation, considering VCAA likes to give long exams and time is of the essence.
true ... however
if you have the same question
and it has
ph range
A= 2
B=3
C=4
D=5
it is hard to say if it is 4 or 5
therefore you must use the KA method.
get what im saying ?
Yeh, pretty sure he does. He was just pointing out that you might not necessarily need the Ka as I showed, and really, it's just that you need to keep an eye out for these things because this is what often distinguishes those who score high and those who don't. Especially from what I've been hearing over the last few years, time has always been a significant constraint in the exams, and using such shortcuts every few questions can save a lot of time overall. And from what I remember, these sorts of shortcuts by deduction/understanding occur quite often.
Home
Help
Search
Login
