A solution of hydrochloric acid of unknown concentration was titrated with 0.16 M NaOH. If a 350-mL sample of the HCl solution required exactly 17 mL of the NaOH solution to reach the equivalence point, what was the pH of the HCl solution?

The correct answer is 2.1

Explanation:

The neutralization reaction involved in the titration is between a strong acid (HCl) and a strong base (NaOH), as follows:

HCl + NaOH → NaCl + H₂O

According to this, 1 equivalent of HCl reacts with 1 equivalent of NaOH. The equivalence point is the point at which the amount of NaOH added reacted completely with the amount of HCl.

moles of acid = moles of base

moles HCl = moles NaOH

Ca x Va = Cb x Vb

Ca = (Cb x Vb)/Va = (0.16 M x 17 mL)/(350 mL) = 7.8 x 10⁻³ M

Since HCl is a strong acid, we calculate the pH of the solution directly from the concentration of acid:

[H⁺]= Ca = 7.8 x 10⁻³ M

pH = -log [H⁺] = -log (7.8 x 10⁻³ M) = 2.11

Therefore, the pH of the HCl solution is 2.1

a. energy is absorbed in the reaction.

if in a given reaction the energy of products is greater than the energy of reactants it means that reaction is endothermic and during the reaction, the energy is absorbed by reactants. in an endothermic reaction, the products have more stored chemical energy than the reactants. and in this reaction the reactants are more stable than products before the compounds with less energy are always more stable.