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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: gleeman on July 19, 2007, 09:28:16 AM

Title: Why does the reaction between HCl + NH3 happen?
Post by: gleeman on July 19, 2007, 09:28:16 AM
Why does the reaction between HCl + NH3 happen?

I know that HCl is ionic and NH3 is non-polar because of symmetry. So has NH3 ionic properties? If has, can this be the reason why the reaction happen?

I appreciate your guidance
Title: Re: Why does the reaction between HCl + NH3 happen?
Post by: vladi307 on July 19, 2007, 09:39:43 AM
NH3 is soluble in the water? What are you thiniking about it?
Title: Re: Why does the reaction between HCl + NH3 happen?
Post by: gleeman on July 19, 2007, 11:11:02 AM
Quote from: vladi307 on July 19, 2007, 09:39:43 AM
NH3 is soluble in the water? What are you thiniking about it?
Yes,
I am thinking why does the following reaction happen:
HCl + NH3 => NH4Cl

Is the main reason that HCl donates proton for NH3 which then turn out ammonium? As a result, Cl- forms salmiac  (NH4Cl) with the product (ammonium).

Could you tell me, is this latter the right reason?

Thanks for your reply!
Title: Re: Why does the reaction between HCl + NH3 happen?
Post by: Erichsen on July 20, 2007, 08:56:20 AM
The reaction happens because delta G < 0.

delta G = delta H - T * delta S

When acid and bases are mixed they usually develop heat (exoterm), which means a negative delta H.
Delta S are a measure of the dissorder of the system. When NH4Cl is formed (salt) the system become more ordered (lattice), which means delta S become negative. But delta H must be more negative then T * delta S.
Hope this helps.

Another way to think about is, HCl is a strong acid, that reacts with almost every bases (NH3 is a weak base, due to its free electronpair, which can accept the hydrogen-ion from HCl ).
Title: Re: Why does the reaction between HCl + NH3 happen?
Post by: gleeman on July 20, 2007, 09:24:16 AM
Quote from: Erichsen on July 20, 2007, 08:56:20 AM
The reaction happens because delta G < 0.

delta G = delta H - T * delta S

When acid and bases are mixed they usually develop heat (exoterm), which means a negative delta H.
Delta S are a measure of the dissorder of the system. When NH4Cl is formed (salt) the system become more ordered (lattice), which means delta S become negative. But delta H must be more negative then T * delta S.
Hope this helps.

Another way to think about is, HCl is a strong acid, that reacts with almost every bases (NH3 is a weak base, due to its free electronpair, which can accept the hydrogen-ion from HCl ).

Thanks a lot!
I really appreciate your guidance!
Both of the ways you illustrated me were the ones I was thinking - I was unable to illustrate them on paper but luckily you managed - thank you!