# Why is hydrochloric acid used in the laboratory in preference to nitric or sulfuric acids?

Nov 26, 2017

Because when it reacts rapidly with $\text{Mg}$, it forms ${\text{H}}_{2}$ in the form of bubbles.

#### Explanation:

The chemical equation used in most cases to show formation of ${\text{H}}_{2}$ is:

${\text{Mg"(s) + 2"HCl"(aq) -> "MgCl"_2(aq) + "H}}_{2} \left(g\right)$

The hydrogen can be detected either by observing the small ${\text{H}}_{2}$ bubbles in the solution or by holding a burning match or a lighter above the liquid container and watch the ${\text{H}}_{2}$ burn with a small 'boom' sound.

Nov 26, 2017

Why? Well probably for convenience....

#### Explanation:

$H C l \left(a q\right)$ is available as the concentrated acid....$\left[H C l\right] = 10.6 \cdot m o l \cdot {L}^{-} 1$, so-called $\text{muriatic acid}$, $\text{spirits of salt}$; bricklayers also use this stuff to wash the mortar off their brickwork.

We can conveniently add acid to water to dilute the concentrated acid (but never the reverse 'cos $\text{if you spit in acid it spits back}$).

Both dilute and concentrated acids can be handled with appropriate care and precautions in the lab (which are?)...and the reaction with a metal generates dihydrogen gas....

$F e \left(s\right) + 2 H C l \left(a q\right) \rightarrow F e C {l}_{2} \left(a q\right) + {H}_{2} \left(g\right) \uparrow$

On the other hand, $\text{sulfuric acid}$ is a NON-OXIDIZING acid, and $\text{nitric acid}$, the other common mineral acid, can generate poisonous and noxious $N {O}_{2}$ upon reduction.