Bronsted - Lowry Theory Of Acids and Bases

[DarylMBCP]

Homework Statement

Some of the books I have state that the equation of...

HCl + NH₃ --> NH₄⁺ + Cl^-

While others state that the above equation should be written as...

HCl + NH₃ --> NH₄Cl

Which one is correct? I think the answer should be the second one since the two compounds would want to reach its stable form by bonding. Am I right?

 

[Borek]

In water or in the gas phase?

 

[DarylMBCP]

What do you mean? Does the products of the reaction stated above depend on their state of matter? Please elaborate.

 

[Borek]

In the gas phase product will be solid substance, in water - dissolved ions. Note, that solid made in the gas phase - once dissolved - will dissociate to exactly the same ions.

 

[DarylMBCP]

In the gas phase product will be solid substance, in water - dissolved ions.

When you say solid substance, are you talking about the NH₄⁺ + Cl^- or NH₄Cl ? How about in other phases? Please elaborate.

 

[Borek]

Sorry, I have no idea what you are asking about.

Are you asking whether solid ammonium chloride is an ionic or covalent? I would expect mostly ionic.

 

[Dadface]

Lets put it another way by reference to a different compound -common salt.
In the solid state the ions are strongly bound together and it is normal to use the formula NaCl.If now the solid is melted or dissolved the ions separate and we could write ,for each,Na+ and Cl-
(how can I write + and - as superscripts?)

 

[Borek]

(how can I write + and - as superscripts?)

With [ sup][ /sup] and [ sub][ /sub] tags. No spaces after opening bracket.

 

[Dadface]

Thank you Borek-I shall try it out.

 

[DarylMBCP]

Sorry for not having phrased my question properly. Haha. I just want to know whether the product(s) of HCl + NH₃ are either the two compounds, NH₄⁺ + Cl^-, or just one compound, NH₄Cl. Are you saying that the product(s) of the reaction depends on its state?

 

[Borek]

You may as well ask whether solid NaCl (kitchen salt) is one compound or two compounds.

I have Canon EOS 400D with 28-105 mm USM lens. I can use the body with other lenses, I can use the lens with other bodies. Is it one compound, or two?

 

[epenguin]

When you are posting isn't there an X² and an X₂ little icon at the top of the answer screen, which people could use to make their posts more legible?

 

[Borek]

Only if you use advanced interface, most people use quick reply.

Which shouldn't stop them from the proper formatting.

 

[DarylMBCP]

I have no idea what you are talking about because what are subsituting the body or the lens with? Please just go straight forward in answering my question because I need it to continue my progress. Thank you.

 

[Borek]

Ionic salts are mixtures of (at least) two different ions. You have asked whether this mixture is one compound (salt), or two (two ions). This is wrong question. This is exactly the same case as with my camera, body and lenses being equivalents of different ions.

Sorry, I have no idea how to explain it in different terms. Looks to me like tou are trying to deal with advanced concept (Bronsted theory), not understanding more basic concepts (ionic salts and dissociation). That's why you have problems.

 

[Dadface]

The two different equations are basically two different ways of saying the same thing.In the solid state,because of their close proximity the charges on the positive ions are balanced by the charges on the negative ions making an overall charge of zero and it is usual to leave out the + and -signs.When the ions are separated,for example by melting,
it is usual to include the + and- signs.It is helpful to include the signs when explaining how the ions bond by electrical attraction but once the bonding is complete and the compound is formed it is normal to leave the signs out.One advantage is that it becomes more economical to write the equation.I have only a very basic knowledge of chemisry so if you are after an answer in terms of the Bronsted Lowry theorem then I don't know what this theory is although I am tempted to look it up.

 

[Borek]

Here you go: Brønsted-Lowry theory of acids and bases.

 

[DarylMBCP]

Oh I finally get what you mean because I have not been realising that Ammonium Chloride is salt. However, from what I have just understood, is it possible to say that generally an acid and a base forms a salt and sometimes water if the base is a metal hydroxide?

 

[Borek]

is it possible to say that generally an acid and a base forms a salt and sometimes water if the base is a metal hydroxide?

Yes, acid and base reaction is one of the most basic methods of salt synthesis. And in inorganic chemistry water is almost always byproduct of this reaction, not sometimes.

 

[DarylMBCP]

Just another quick example to check my understanding;

Nitric acid and Ammonia forms Ammonium Nitrate

where Ammonium Nitrate is a salt?

 

[Borek]

Yes. No water as a byproduct, but that's characteristic of ammonia.

At some point in time it was assumed that ammonia does react with water creating ammonium hydroxide (NH₄OH) which dissociates and makes its solutions basic, and when it reacts with acids water is a byproduct. Trick is, it is very difficult to devise experment that will let you differentiate between this scenario and scenario in which ammonia is just dissolved and reacts accepting proton (Bronsted base). But it was done and ammonium hydroxide was put to rest into the box next to unicorns and mermaids

 

[DarylMBCP]

Haha, thnks again for helping me with this question. However, a new question has hatched in my mind although it is not about acids and bases; If there is what is the charge of a transition metal that is able to vary its charge if it does not have any numeral behind it when written in its chemical name?

For example, for Silver Chloride, is the chemical formula AgCl since Ag has only a 1+ charge there is no numeral like (I) or (II) behind it? Is this true?

 

[Borek]

If there is what is the charge of a transition metal that is able to vary its charge if it does not have any numeral behind it when written in its chemical name?

it is either your English or my English, but I have no idea what you are asking about.

For example, for Silver Chloride, is the chemical formula AgCl since Ag has only a 1+ charge there is no numeral like (I) or (II) behind it? Is this true?

It is more important when you use names instead of formulae - SO₂ and SO₃ are unambiguous, while sulfur oxide is. But sulfur (IV) oxide and sulfur (VI) oxide are unambiguous again.

And silver can be +2 and +3 as well

 

[DarylMBCP]

Do you mean that Sliver Chloride can either have 2+ or 3+ charge although there may not be (II) or (III) written after it like Silver (II) or Silver(III)?

 

[Borek]

No, not in chloride, just there are known compounds of Ag²⁺ and Ag³⁺ presence is confirmed in solutions of some strong oxidizing agents.

Could be there is more to it but I don't remember details and can't check it atm.

And silver chloride can't have +2 charge, it is silver cation that has a charge, salt molecule is electrically neutral.

 

[DarylMBCP]

Kk, I think I got it. Thnks very much for your help so far.