Question

Which has higher concentration of $ {H^ + } $ ions $ 1M $ $ HCl $ or $ 1M $ $ C{H_3}COOH $ ?

Answer 1

Hint: The higher concentration of $ {H^ + } $ ions depends upon the acid's ability to dissociate into the aqueous solution. This ability to dissociate ions further depends upon whether the acid is a strong acid or a weak acid.

Complete answer:
Here the given molar solution is the same in amount, therefore it will not have an effect on the concentration of the $ {H^ + } $ ions. As mentioned in the hint, one must see whether an acid is strong or weak acid because the strong acid will dissociate completely in the aqueous solution whereas the weak acid will dissociate partially.
One must know what acid dissociation or acid dissociation constant mean. It is a quantitative measure of the strength of an acid in solution. It is also known as the acidity constant or acid-ionisation constant. $ H\;Cl $ is a strong acid. $ H\;Cl $ with one ionisable $ hydrogen $ will be completely ionized in aqueous solutions, therefore the $ hydrogen $ ion concentration of these solutions is equal to the molar concentration of the acid. When $ 1M $ $ H\;Cl $ is dissolved in $ 1L $ of water, $ 1M $ of $ {H^ + } $ and $ 1M $ of $ C{l^ - } $ is formed by dissociation.
The $ hydrogen $ ion concentration of an aqueous solution of a weak acid depends on the value of its acid dissociation constant and is always less than the value of concentration of the weak acid. Since $ acetic{\text{ }}acid $ is a weak ionises into $ hydrogen $ ion concentration, but only a small fraction of the molecule. Most of it remains un-ionised $ acetic{\text{ }}acid $ . The acid dissociation constant is much less than $ 1M $
Therefore $ H\;Cl $ will have higher concentration of $ {H^ + } $ ions.

Note:
Acids, bases and salts dissociate into electrolytes when placed in water. Acids dissociate into $ {H^ + } $ ions, bases dissociate into $ O{H^ - } $ ions and salts dissociate into a cation and an anion. Also the acid strength is solvent dependent.