# Why is CH3CH2NH3Cl acidic?

Why is $\ce{CH3CH2NH3Cl}$ acidic?

I know that it has something to do with how it is formed from a weak alkaline, but I cannot identify which acid and base it is formed from.

• Its a salt of weak base and strong acid so on hydrolysis it forms acidic solution – JM97 Sep 1 '16 at 13:56
• Have you tried drawing it? What do you think ought to be the cation and anion parts when dissociating in water? – SCH Sep 1 '16 at 14:03
• As, mentioned its a salt formed by reacting Ethyl amine with HCl, – Khan Sep 1 '16 at 14:18

## In short

$\ce{CH3CH2NH3Cl}$ is acidic because it is formed from a strong acid ($\ce{HCl}$) and a weak base ($\ce{CH3CH2NH2}$).

## Elaborated

Notice that this compound is ionic, comprising $\ce{CH3CH2NH3+}$ cation and $\ce{Cl-}$ anion.

I mentioned that $\ce{CH3CH2NH2}$ is weak, meaning that this reaction is reversible:

$$\ce{CH3CH2NH2 + H2O <=> CH3CH2NH3+ + OH-}\tag1$$

In an acidic environment, we can rewrite it as:

$$\ce{CH3CH2NH2 + H3O+ <=> CH3CH2NH3+ + H2O}\tag2$$

Therefore, when $\ce{CH3CH2NH3Cl}$ dissolves in water, there would be initially an equal amount of $\ce{CH3CH2NH3+}$ and $\ce{Cl-}$ in terms of number of moles.

Using equation $(2)$, we know that $\ce{CH3CH2NH3+}$ will react with water reaching an acidic equilibrium.

Note that there is no $\ce{OH-}$ to start with (very little in reality), so equation $(1)$ is not applicable.

Therefore, the following species would be present:

• $\ce{CH3CH2NH3+}$
• $\ce{CH3CH2NH2}$
• $\ce{H2O}$
• $\ce{H3O+}$
• $\ce{Cl-}$

Now it is apparent that $\ce{H3O+}$ makes it acidic.

• No mistakes. I wish there were more first answers like this! Have my upvote! – Jan Sep 1 '16 at 22:12