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hslove142331
Mar 26, 2010, 11:13 PM
Consider the following compounds and suppose that 0.5 M solutions are prepared of each: NaI, KF, (NH4)2SO4, KCN, KC2H3O2, CsNO3, and KBr.

I really don't know how to figure out that which solutions are acidic or basic or neutral.

Please help me that how can I figure that out.

Thank you

Unknown008
Mar 26, 2010, 11:32 PM
You can make use of sodium carbonate or potassium chromate (VI) to test for acidity.

Acids will react with sodium carbonate to form carbon dioxide (if the acid is stronger than carbonic acid) and will react with yellow potassium chromate (VI) to form the orange potassium dichromate (VI)

For bases, you can make them react with phenol, a white solid which is acidic. If the phenol dissolves, then the solution is alkaline.

If the substance doesn't react with any of the two 'experiments' so to say, then it's neutral.

But if you want to say like that which of them are acidic and which of them are neutral, you have to look at what ions they are made up of.

NaI - consists of Na+ and I-. Na+ comoes from NaOH (strong base) and I- comes from HI (weak acid). Hence, NaI is more basic.

KF - Made from KOH and HF. Both are strong base and acid respectively, hence, the resulting solution is neutral.

etc.

hslove142331
Mar 27, 2010, 11:46 AM
NaI - consists of Na+ and I-. Na+ comoes from NaOH (strong base) and I- comes from HI (weak acid). Hence, NaI is more basic.

KF - Made from KOH and HF. Both are strong base and acid respectively, hence, the resulting solution is neutral.


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Sorry, I am still confusing that which one is more strong or not...
I mean... which one is strong acid or weak acid, strong basic or weak basic... and neutral.
Could you please give more easier explain for me?
Thank you ;)

Unknown008
Mar 28, 2010, 12:54 AM
In fact, that's already very simple, the actual way to determine that is much more complicated.

Ok, say a strong acid is denoted by '--' (minus minus)
A strong base is denoted by '++' (plus plus)

Then a weak acid will be '-' and a weak base '+'

If you have a strong acid and a weak base, you'll have '--++' the minus cancel out the plus giving neutral.

If you have a strong acid and a weak base, you'll have '--+' giving '-' which is a weak acid.

If you have a weak acid and a strong base, you'll have '-++' giving '+' which is a weak acid.

If you have a weak acid and a weak base, you'll have '-+' giving a neutral salt.

Of course, the best way is to test for their acidity or basicity using some reagents.

hslove142331
Mar 28, 2010, 02:16 AM
Okay... I am still don't understand,but thank you so much

InfoJunkie4Life
Mar 30, 2010, 09:47 PM
pKa and LogP Measurements (http://www.raell.demon.co.uk/chem/logp/logppka.htm)

Unknown008
Mar 31, 2010, 11:05 PM
Ok, I'll proceed to the question answer method of mine then ;)

You know NaOH and HCl. The salt they form is NaCl.

Is NaOH a strong base?
Is HCl a strong acid?
Then, what would be NaCl? More basic or more acidic?

Post your answer, according to what you think is good. In either case, you'll be learning.

wellduh
Apr 25, 2011, 09:50 PM
How can you be an expert when that is so wrong.

wellduh
Apr 25, 2011, 09:51 PM
HI is the strong acid. This makes NaI neutral and KF acidic respectively.

Unknown008
Apr 26, 2011, 09:19 AM
Indeed, now I realise my mistake. I posted that last year and I learned of my mistakes. Next time, read the date the thread was made before answering.