A solution of pyridinium bromide has a pH of 3.00. What is the concentration of the pyridinium cation at equilibrium, in units of molarity? Express molarity to two decimal places.

The concentration of the pyridinium cation at equilibrium is 1.00×10⁻³ M

Explanation:

In water we have

C₅H₅NHBr + H₂O ⇒ C₅H₅NH+ + Br−

Pyridinium Bromide (C₅H₅NHBr) Dissociates Completely  Into C₅H₅NH+ And Br− as such it is a strong Electrolyte.

Therefore the number of moles of positive ion produced per mole of C₅H₅NHBr  is one

pH = - log [H₃O⁺] Therefore 10^-pH = [H₃O⁺] = concentration of C₅H₅NHBr

= 10⁻³ = 0.001M = concentration of C₅H₅NHBr

The concentration of C₅H₅NHBr is = 1.00×10⁻³ M to two places of decimal