Predictions for Chemistry 2014 HSC? (3 Viewers)

seventhroot

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Stop derailing

New question

Explain, using a relevant equation, why ammonium chloride is an acidic salt.
Ill have another go :D

Iirc, the composition is NH4Cl and when you do the pH thing, it is <7 so its acidic and it is a salt because chlorides are salts?
 

enigma_1

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Ill have another go :D

Iirc, the composition is NH4Cl and when you do the pH thing, it is <7 so its acidic and it is a salt because chlorides are salts?
LOOOOOOOOOOOOOOOOOOOOOOL I'm not even gonna..
 

QZP

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Ammonium chloride is formed from ammonia (or ammonium hydroxide) and hydrochloric acid. The ammonium ion acts as a weak Bronsted–Lowry acid when dissolved in water. This equilibrium lies to the left as the hydronium ion is a stronger acid than ammonium ions and NH3 is a stronger base than water. The final solution is mildly acidic due to the presence of the hydronium ion.

NH4+(aq) + H2O(l) <> NH3(aq) + H3O+ (aq)
THIS IS THE PROBLEM IM HAVING. You are assuming something. How do you know NH4+ comes from ammonia and Cl- comes from hydrochloric acid? That is just one example. If you write that in your exam solution I'm sure you'd lose marks
 
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enigma_1

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THIS IS THE PROBLEM IM HAVING. You are assuming something. How do you know NH4+ comes from ammonia and Cl- comes from hydrochloric acid? If you write that in your exam solution I'm sure you'd lose marks
NH3 + H20 --> NH4+ + OH-

Then you say it releases NH4+ in water which is the WEAK conjugate acid of NH3.

Then

HCL + H2O ---> CL- + H3O+

Again HCL dissociates in water and produces it's EXTREMELY WEAK conjugate base Cl- chloride ion.

Now since WEAK>EXTREMELY WEAK


:. Be like the NH4Cl is acidic because it consists of a weak conjuaget acid NH4+ and EXTREMELEY weak conjugate base CL-

and you can also show iy

NH4Cl ---> NH4+ + Cl- (which is the dissociation of NH4Cl in water)
 
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QZP

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Oh crap!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! I said NH4+ is a strong conj. acid of a weak base T__T It's actually weak conj. acid of a weak base hahaha (your solution made me realise my misunderstanding). Thanks enigma_1
 
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THIS IS THE PROBLEM IM HAVING. You are assuming something. How do you know NH4+ comes from ammonia and Cl- comes from hydrochloric acid? That is just one example. If you write that in your exam solution I'm sure you'd lose marks
That's how most sample answers are written.

Excel does it, my teacher taught me as well.
 

enigma_1

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Oh crap!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! I said NH4+ is a strong conj. acid of a weak base T__T It's actually weak conj. acid of a weak base hahaha (your solution made me realise my misunderstanding). Thanks enigma_1
no worries :)

just a reminder of stuff

if you have a WEAK acid/base, then it's conjugate is also WEAK
if EXTREMELY WEAK acid/base, then it's conjugate is STRONG
if STRONG acid/base, then it's conjugate is EXTREMELY WEAK

and that's it.
 

enigma_1

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So they are both great books.

Thanks enigma :DD
m666 Math sin focus ---> can't you see?? Clearly it says in the title of the book that it is a "sin". How much more explicit does it need to get?

Also, add "s" to the front of "excel" and you get something used as a marketing ploy. That's probs the only reason these books are sold.

You guys are making me insane, I've started analysing MIF... :spzz:
 

seventhroot

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m666 Math sin focus ---> can't you see?? Clearly it says in the title of the book that it is a "sin". How much more explicit does it need to get?

Also, add "s" to the front of "excel" and you get something used as a marketing ploy. That's probs the only reason these books are sold.

You guys are making me insane, I've started analysing MIF... :spzz:
You know what they say, MIF is a great book
 

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