Chemistry..Unit..4...(6CH04)

[5402410]

The..exam..is..close..and..I..didn't...find....a....thread...for...this...exam...
So...I...decided..to....create..one
How...are...you....guys...preparing?!

 

[ameer batarseh]

hey man, can u explain this question:
Which of the following solutions, when mixed, would make a buffer with pH
more than 7?
A Methanoic acid and sodium methanoate.
B Sodium hydroxide and sodium chloride.
C Ammonia and ammonium chloride.
D Ammonium chloride and ammonium ethanoate.
what is the answer and why??????

 

[étudiante]

hey man, can u explain this question:
Which of the following solutions, when mixed, would make a buffer with pH
more than 7?
A Methanoic acid and sodium methanoate.
B Sodium hydroxide and sodium chloride.
C Ammonia and ammonium chloride.
D Ammonium chloride and ammonium ethanoate.
what is the answer and why??????

A - not possible as we need a pH MORE dan 7 (so we need an alkali)
B - Alkali is present but its a strong one, for buffers u need a weak alkali, so this is also not acceptable
C - Ammonia is a weak base and ammonium chloride is an appropriate salt so it is the correct answer
D - Both are salts so not possible...

Therefore the answer is C

 

[ameer batarseh]

A - not possible as we need a pH MORE dan 7 (so we need an alkali)
B - Alkali is present but its a strong one, for buffers u need a weak alkali, so this is also not acceptable
C - Ammonia is a weak base and ammonium chloride is an appropriate salt so it is the correct answer
D - Both are salts so not possible...

Therefore the answer is C

For D isn't ammonium a strong conjugate acid, so the ph must be lower than 7 as ammonia is a weak base!!!!!
and why isn't it A it is a weak acid (methanoic) and a strong conjugate base (methanoate)?????

 

[étudiante]

For D isn't ammonium a strong conjugate acid, so the ph must be lower than 7 as ammonia is a weak base!!!!!
and why isn't it A it is a weak acid (methanoic) and a strong conjugate base (methanoate)?????

D is not possible as both are salts! We need to have a salt along with a weak acid or a weak alkali (ONLY a conjugate wont do)

We need a pH MORE than 7 so we need to have an alkali and its salt (even tho we dont do alkaline buffers in our course, we need to infer dat since acidic buffers have a pH less dan 7, alkaline buffers should have a pH more dan 7) thats why A is not possible

 

[ameer batarseh]

D is not possible as both are salts! We need to have a salt along with a weak acid or a weak alkali (ONLY a conjugate wont do)

We need a pH MORE than 7 so we need to have an alkali and its salt (even tho we dont do alkaline buffers in our course, we need to infer dat since acidic buffers have a pH less dan 7, alkaline buffers should have a pH more dan 7) thats why A is not possible

i wrote it wrong i meant for C
but i got the picture thx a lottt

 

[étudiante]

ok thx alooott

No need for dat Just remeber me in ur prayers ^_^