Question

______ increases with the increase in ${H^ + }$ ions.

Answer 1

We know A acid is an atom or particle able to do either giving a proton (i.e., hydrogen particle, ${H^ + }$), known as a Bronsted–Lowry acid, or, equipped for shaping a covalent bond with an electron pair, known as a Lewis acid.
The primary classification of acids is the proton contributors, or Bronsted–Lowry acids. In the uncommon instance of fluid arrangements, proton benefactors structure the hydronium particle ${H_3}{O^ + }$ and are known as Arrhenius acids. Bronsted and Lowry summed up the Arrhenius hypothesis to incorporate non-watery solvents. A Bronsted or Arrhenius acid for the most part contains a hydrogen molecule clung to a substance structure that is still enthusiastically ideal after loss of ${H^ + }$.

Complete Answer:
The Strength of acid increases as the number of ${H^ + }$ particles increases.
Acid-
The sharp taste is the most widely recognized attribute of acid. An acid is a material that in its watery arrangement produces the ionizable hydronium particle ${H_3}{O^ + }$. It causes the blue litmus paper to become red.
$H + {H_2}O \to {H_3}{O^ + }$

Note:
Now we can discuss about the PH of Acids and Bases-
To track down the numeric worth of the degree of acidity or basicity of a substance, the pH scale (wherein pH means 'capability of hydrogen') can be utilized. The pH scale is the most well-known and believed approach to gauge how acidic or essential a substance is. A pH scale measure can shift from $0$ to$14$ , where $0$ is the most acidic and $14$ is the most fundamental substance. Another approach to check if a substance is acidic or fundamental is to utilize litmus paper. There are two sorts of litmus paper accessible that can be utilized to distinguish acids and bases – red litmus paper and blue litmus paper. Blue litmus paper becomes red under acidic conditions and red litmus paper becomes blue under fundamental or basic conditions.