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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Chemistry => Topic started by: MattZhang on July 07, 2011, 02:12:11 pm

Title: Memorising constants
Post by: MattZhang on July 07, 2011, 02:12:11 pm

Hiya,
     do you guys know if we have to memorise the acidity constants for common acids for the end of year exam? In the data book the acidity constants of some weak acids are given but theres nothing about strong acids. Also, do we have to memorise the ionisation constants of water for different temperatures or should we just assume it is always = 10^-14?

Title: Re: Memorising constants
Post by: stonecold on July 07, 2011, 02:21:56 pm

No, you don't have to memorise them.  That is what the book is for.

And strong acids have very large acidity constants, because ionisation is close to 100%.

You only need to know the ionisation constant for water at 25 degrees.

But, you should know that the self ionisation of water is an endothermic reaction and be able to answer questions such as

Water stored at 40 degrees would
A.  Have a pH = 7 and be neutral
B.  Have a pH > 7 and be neutral
C.  Have a pH > 7 and be alkaline
D.  Have a pH < 7 and be neutral
E.  Have a pH < 7 and be acidic

Title: Re: Memorising constants
Post by: MattZhang on July 07, 2011, 02:32:48 pm

Cheers bro :D
Also, for that question you put, would the answer be D?

Title: Re: Memorising constants
Post by: stonecold on July 07, 2011, 02:33:31 pm

Quote from: MattZhang on July 07, 2011, 02:32:48 pm

Cheers bro :D
Also, for that question you put, would the answer be D?

Sure is!  :D

Title: Re: Memorising constants
Post by: MattZhang on July 07, 2011, 02:35:59 pm

thanks mate, been real helpful  :)