Question

Someone please explain this to me.
Which statements are true?
Ammonia and chlorine react in the gas phase.

8NH3 + 3Cl 2 → N2 + 6NH4Cl

Which statements are correct?
1 Each nitrogen atom is oxidised.
2 Each chlorine atom is reduced.
3 Ammonia behaves as a base.

Answer 1

I thought 1 and 2 are true but the answer says it's 2 and 3 that are true. Why? How is NH3 acting as a base here? @ganeshie8 @JFraser

Answer 2

Nitrogen is getting oxidised from -3 in NH3 to 0 in N2.

Answer 3

NH3 is excepting proton

Answer 4

if you look at the ammonia reactant, it becomes the ammonium ion as a product. by that behavior, the ammonia accepts a proton, and acts as a base. I don't really like the question, but that seems to be the rationalization to me

Answer 5

Bronsted-Lowry acid - is a proton donor
and Bronsted-Lowry base is proton acceptor

Answer 6

But NH3 is accepting a proton from what reactant? I mean the other reactant is just chlorine?

Answer 7

Only in aqueous ammonia does NH3 accept a proton from H2O to give NH4+ ions. And they have specified in this question that NH3 is in gas phase.

Answer 8

maybe Cl is from an acid?

Answer 9

@thushananth01

Answer 10

For the first two points, consider the oxidation states of each atom.

N goes from -3 in NH3 to 0 in N2 (it is oxidized)
Cl goes from 0 in Cl2 to -1 in NH4Cl (it is reduced)

Both #1 and #2 seem right based on this...but if you look closely, you have N atoms in NH4Cl, and their oxidation state is still -3! This means some N atoms were not oxidized, and so #1 is wrong.

For #3, we need to think about Lewis acids and bases (i.e. ELECTRON donors and acceptors) rather than Bronsted-Lowry acids and bases (i.e. PROTON donors and acceptors). Based on our redox reactions above, we can see that NH3 is an electron donor and therefore a Lewis base. Chlorine, on the other hand, is an electron acceptor and so is a Lewis acid.

#2 and #3 are correct, but #1 isn't. Hope that helps!

Answer 11

@matt101 : Okay, I got your first 2 points.
But I'm still not convinced about the Lewis base thing.
Like in reaction of NH3 and HCl, NH3 acts as lewis base and HCl reacts as Lewis acid, thus forming NH4Cl.
However, this reaction is of NH3 with Cl2. How can Cl2 accept electrons to form NH4Cl?

Answer 12

We know this is a Lewis acid/base situation because we aren't in water (as mentioned before) and there are no clear proton donors AND acceptors here. Based on the changes in oxidation states, we can see that Cl2 still acts as an electron acceptor, even without knowing anything about this specific reaction.

I can't explain exactly how the electron movements work for this particular reaction because this isn't my area of expertise, but what I can say is that this reaction probably involves multiple steps and reaction intermediates during which the electron accepting/donating is perhaps more obvious.

Answer 13

Okay, thank you so much @matt101 . (:

Answer 14

NH3 + H+ -----> NH4 +( NH3 act as a bronsted base, because it accepts a proton which means it behaves as a base)

Answer 15

0.5Cl2 +e- -----> Cl -