Chem: Question of the day 06/21

[Awuah29]

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What is the congugate base of NH3
A NH4-
B NH2-
C H30+
D OH-
E Cl-


The answer is D. Can someone explain? Thought B was the right answer

 

[DrTacoElf]

OK in this sitiuation NH3 is acting as a BASE according to the Bronsted Lowry Definition (picking up a proton). Thus NH4+ is its conjugate acid.


The reaction is as follows NH3 + H20 ---> NH4+ + OH-


Thus OH- is the conj. base of H20.

 

[Eddie830]

I agree, the answer should be B

 

[AshDDS2B]

Conjugate acids and bases are always related by the gain/loss of H(+).
e.g. NH3(g) + H2O(l) = NH4+(aq) + OH-(aq)

base (acid) conj. acid (conj. base)

NH3 is a Bronsted-Lowry base: H(+) acceptor and an Arrhenius base: releases OH-

Base + H+ = conjugate acid

Acid - H+ = conjugate base

Thus, if you (NH3) - ( a proton ) = NH2.

Are you sure D is the correct answer ?

 

[ems5184]

OK in this sitiuation NH3 is acting as a BASE according to the Bronsted Lowry Definition (picking up a proton). Thus NH4+ is its conjugate acid.


The reaction is as follows NH3 + H20 ---> NH4+ + OH-


Thus OH- is the conj. base of H20.

Going based on what you said, DrTacoElf, why couldnt Cl- be the conjugate base?

NH3 + HCl ---> NH4+ + Cl-
NH3 - base, HCl - acid, NH4+ - conjugate acid, Cl- - conjugate base?

My reasoning is correct isnt it?

 

[DrTacoElf]

Going based on what you said, DrTacoElf, why couldnt Cl- be the conjugate base?

NH3 + HCl ---> NH4+ + Cl-
NH3 - base, HCl - acid, NH4+ - conjugate acid, Cl- - conjugate base?

My reasoning is correct isnt it?

yeah in that reaction you just wrote.

 

[phosphorylation]

I'm pretty sure the answer D that you have is incorrect, I've heard of a couple of errors in these books. I'm almost possitive its B. They specifically want the conjugate base, not the conjugate acid. for the answer to be OH, that would be almost impossible...on the other hand, i guess I'm either totally right, or I need some major general chemistry review...

 

[dreamaloud]

http://vms.www.uwplatt.edu/~sundin/363-8/6380116a.htm

i agree with phosphorylation, i doubted myself b/c everyone else thought differently.....i think the website clears it up. 🙂