Question

A student conducts a titration of 50 mL of HCl with 1.00 M NaOH. The pH at the equivalence point is

Basic

Neutral

Acid

Answer 1

The titration given is an acid-base titration involving reaction of HCl, the acid with NaOH, the base, forming a salt which is a combination of the conjugate base of the acid (chloride ion) and conjugate acid of the base (sodium ion) giving sodium chloride. Also, the abstraction of proton from HCl by the hydroxyl ion from NaOH results in formation of water molecule. The net reaction here can be written as HCl + NaOH -----> NaCl + H₂O.

pH is a measure of concentration of protons in a solution and pOH is a measure of concentration of hydroxyl ions. pH and pOH are interrelated as pH = 14 - pOH. pH values between 0 - 7 show an acidic medium; above 7 shows a basic medium and pH of exactly 7 shows a neutal medium. At the equivalence point, all the protons released by the HCl will be consumed by precisely equinormal quantity of NaOH resulting in the absence of both protons and hydroxyl ions. Since these two species alone are responsible for producing pH in a solution and they are both absent at the equivalence point, the pH of the solution will be neutral.