# What is the difference between a concentrated and a dilute acid?

Jun 8, 2017

A concentrated acid is a species whose concentration is (typically) GREATER than $1 \cdot m o l \cdot {L}^{-} 1$; whereas a...........

#### Explanation:

..........whereas a dilute acid is a species whose concentration is LESS than $1 \cdot m o l \cdot {L}^{-} 1$. Note that this definition of acidity does not take into account whether protonolysis is complete or incomplete; i.e. $H F$ and $H O A c$ can BOTH be quite concentrated. Nevertheless, these are both quite weak Bronsted acids, i.e. the equilibrium......

$H X \left(a q\right) + {H}_{2} O \left(l\right) r i g h t \le f t h a r p \infty n s {H}_{3} {O}^{+} + {X}^{-}$

............lies somewhat to the left.

For sulfuric acid, the equilibrium lies to the right........

${H}_{2} S {O}_{4} \left(a q\right) + 2 {H}_{2} O \left(l\right) \rightarrow 2 {H}_{3} {O}^{+} + S {O}_{4}^{2 -}$

Given the definition advanced above, any solution of ${H}_{2} S {O}_{4} \left(a q\right)$ whose concentration is LESS than $0.5 \cdot m o l \cdot {L}^{-} 1$ with respect to ${H}_{2} S {O}_{4} \left(a q\right)$ would therefore be classified as a dilute acid. Why
$0.5 \cdot m o l \cdot {L}^{-} 1$ and not $1.0 \cdot m o l \cdot {L}^{-} 1$. You should check your syllabus with regard to this definition; the cut-off point is arbitrary.

An important practical tip when you deal with conc. acids: when you dilute a strong acid with water IT IS ALWAYS ACID TO WATER, and NEVER WATER TO THE ACID. Why? Because if you spit in strong acid it will spit back.