How do I write out the chemical reaction of ammonia with strong acid?


> 
> Write equations for the reactions of each of: (a) nitric acid (b) sulfuric acid \*(c) hydroiodic acid, with each of: (i) sodium hydroxide (ii) zinc oxide (iii) ammonia.
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So, the reaction of nitric acid with sodium hydroxide and zinc oxide is simple because I know that acid + base = salt + water. Therefore:


$$
\begin{align}
\ce{HNO3(aq) + NaOH (aq) &-> NaNO3 (aq) + H2O (l)}\\
\ce{2HNO3(aq) + ZnO (s) &-> Zn(NO3)2 (aq) + H2O (l)}
\end{align}
$$


It makes sense. In the second part, for example, $\ce{Zn}$ is 2+ and $\ce{H}$ is -1. So using the criss-cross method, you get $\ce{Zn(NO3)2}$ and water. I understand this.


However, with ammonia:


$$\ce{HNO3(aq) + NH3 -> NH4NO3}$$


How am I supposed to know this equation? It's not metal + acid = salt + water. Is there word equations for *everything*?





> 
> In the second part, for example, $\ce{Zn}$ is 2+ and $\ce{H}$ is -1. So using the criss-cross method, you get $\ce{Zn(NO3)2}$ and water. I understand this.
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I don't agree on the -1 for hydrogen, let's look again at that example:


$$\ce{2HNO3(aq) + ZnO(s) -> Zn(NO3)2(aq) + H2O}$$


**Metal oxides**, such as zinc oxide, **are basic anhydrides**. 


Imagine that 


1. $\ce{ZnO}$ was made by heating $\ce{Zn(OH)2}$ until it loses water:


$$\ce{Zn(OH)2 ->[\Delta] ZnO(s) + H2O}$$


2. $\ce{ZnO}$ is a salt of $\ce{Zn^2+}$ and $\ce{O^2-}$


The reaction between nitric acid and zinc oxide and just a neutralization reaction between two protons and $\ce{O^2-}$ (which, as such, isn't present in solution).


Now for the reaction with ammonia: For this you may want to remember that there are different acid-base theories: The one that helps here is the *Bronsted-Lowry* theory:


* **Acids are proton donors**


$\ce{HNO3}$ definitely is that.


* **Bases are proton acceptors**


How can something else other than the $\ce{OH-}$ that you knew and the $\ce{O^2-}$ from $\ce{ZnO}$ be a proton acceptor = form a bond to a (proton)? 


Is that possible if this acceptor doesn't even have a negative charge? 


(*Yes, otherwise I wouldn't buld up the tension like in a suspense story :D*)


If the proton can't provide the electrons for the bond, the acceptor has to deliver them! And that can happen in the form of an electron pair, a double filled, non-bonding orbital.


Therefore a reaction, such as 


$$\ce{H+ + NH3 <=> NH4+}$$


is perfectly valid. The rest of the example is just arranging the counter ions. 


 2


> 
> How am I supposed to know this equation?
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You have to *memorise* it. In aqueous solution, $\ce{NH3}$ deprotonates a small fraction of the water to give ammonium and hydroxide


$$
 \ce{NH3 + H2O <=> NH4+ + OH−} \, ,
$$


and while it is usually impossible to isolate $\ce{NH4OH}$ itself, the above mentioned ions are there in the solution. And thus, an aqueous solution of $\ce{NH3}$ is a weak base and reacts with acids in the similar way as other weak bases.



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> How can I access all the word equations in chemistry so I am able to write every single equation given to me like these.
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Again, learning general principles plus memorising all the special cases & exceptions is the only way.$%edit$


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