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conjugate acid- base pairs

The student adds methanoic acid, HCOOH (ka=n 1.82 x 10-4 mol dm-3) to butanoic acid. A reaction takes place to form an equilibrium mixture containing two acid base pairs. Complete the equilibrium below and label the conjugate acid base pairs.

HCOOH + CH3(CH2)2COOH (equilibrium sign) ................ + ................

Is this right?

HCOOH + CH3(CH2)2COOH (equilibrium sign) HCOOH2 + CH3(CH2)2COO-
(edited 11 years ago)
Reply 1
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AtomicMan
13
What are the Ka values for the acids?
Reply 2
Avatar for tazmaniac97
tazmaniac97
OP
12
Original post by AtomicMan
What are the Ka values for the acids?


It's 1.82 x 10-4, sorry I forgot to add it in the OP. I'll add it now.
Reply 3
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AtomicMan
13
Original post by tazmaniac97
It's 1.82 x 10-4, sorry I forgot to add it in the OP. I'll add it now.


Whats the Ka for butanoic acid? This all depends on their relative Ka values. What do you know about the acid-dissociation constant?
Reply 4
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tazmaniac97
OP
12
Original post by AtomicMan
Whats the Ka for butanoic acid? This all depends on their relative Ka values. What do you know about the acid-dissociation constant?


1.51 x 10-5 mol dm-3
Reply 5
Avatar for tazmaniac97
tazmaniac97
OP
12
Original post by AtomicMan
Whats the Ka for butanoic acid? This all depends on their relative Ka values. What do you know about the acid-dissociation constant?


Oh I think I get it now, the strongest acid would be the one that dissociates, so the correct answer is:

HCOOH + CH3(CH2)2COOH (equilibrium sign) HCOO- + CH3(CH2)2COOH2

Am I right?
Reply 6
Avatar for AtomicMan
AtomicMan
13
Original post by tazmaniac97
1.51 x 10-5 mol dm-3


Right ok, acids with higher Ka's will basically dissociate more often to release H+ ions. So butanoic acid would dissociate more than methanoic acid, so butanoic acids acts as the acid and protonates methanoic acid.

Your answer is correct :smile:

Original post by tazmaniac97
Oh I think I get it now, the strongest acid would be the one that dissociates, so the correct answer is:

HCOOH + CH3(CH2)2COOH (equilibrium sign) HCOO- + CH3(CH2)2COOH2

Am I right?


No, you were right at first :smile: A stronger acid will have a higher Ka value.
(edited 11 years ago)
Original post by AtomicMan
Right ok, acids with higher Ka's will basically dissociate more often to release H+ ions. So butanoic acid would dissociate more than methanoic acid, so butanoic acids acts as the acid and protonates methanoic acid.

Your answer is correct :smile:



No, you were right at first :smile: A stronger acid will have a higher Ka value.


methanoic acid is the stronger and so disociates providing a proton for the butanoic acid.
Original post by tazmaniac97
Oh I think I get it now, the strongest acid would be the one that dissociates, so the correct answer is:

HCOOH + CH3(CH2)2COOH (equilibrium sign) HCOO- + CH3(CH2)2COOH2

Am I right?


This is correct ...
Reply 9
Avatar for AtomicMan
AtomicMan
13
Original post by charco
methanoic acid is the stronger and so disociates providing a proton for the butanoic acid.


Woops, read the -5 as a -3 :lol: Yes, methanoic acid is stronger.

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