When 25.00 mL of HNO3 are titrated with Sr(OH)2, 58.4 mL of a 0.218 M solution are required. (

When 25.00 mL of HNO3 are titrated with Sr(OH)2, 58.4 mL...

When $25.00 \mathrm{~mL}$ of $\mathrm{HNO}_{3}$ are titrated with $\mathrm{Sr}(\mathrm{OH})_{2}, 58.4 \mathrm{~mL}$ of a $0.218 M$ solution are required. (a) What is the $\mathrm{pH}$ of $\mathrm{HNO}_{3}$ before titration? (b) What is the $\mathrm{pH}$ at the equivalence point? (c) Calculate $\left[\mathrm{NO}_{3}^{-}\right]$ and $\left[\mathrm{Sr}^{2+}\right]$ at the equivalence point. (Assume that volumes are additive.)

When $25.00 \mathrm{~mL}$ of $\mathrm{HNO}_{3}$ are titrated with $\mathrm{Sr}(\mathrm{OH})_{2}, 58.4 \mathrm{~mL}$ of a $0.218 M$ solution are required.
(a) What is the $\mathrm{pH}$ of $\mathrm{HNO}_{3}$ before titration?
(b) What is the $\mathrm{pH}$ at the equivalence point?
(c) Calculate $\left[\mathrm{NO}_{3}^{-}\right]$ and $\left[\mathrm{Sr}^{2+}\right]$ at the equivalence point. (Assume that volumes are additive.)

Key Concepts

Equivalence Point

The equivalence point in a titration is the stage at which the amount of titrant added is exactly enough to completely react with the analyte, leaving neither in excess. For strong acid-strong base titrations, this point typically corresponds to a neutral pH, since the resulting ions do not further react with water, assuming no additional factors such as dilution significantly alter the pH.

pH Calculation for Strong Acids

For a strong acid, because it dissociates completely in water, the hydrogen ion concentration is directly equal to the molar concentration of the acid. The pH is calculated by taking the negative logarithm (base 10) of this concentration. This concept is fundamental when determining the pH of the solution before any titrant is added.

Dilution Effects in Titration

During a titration, the overall volume of the solution changes as the titrant is added, which leads to a dilution of all ions present in the solution. When calculating the final concentrations of spectator ions formed in the reaction, it is important to account for the total volume after the addition of the titrant. This dilution effect must be considered to accurately determine the molarity of ions in the final solution.

Acid-Base Titration

Acid-base titration is an analytical technique used to determine the concentration of an acid or base by gradually adding a reagent of known concentration until the reaction reaches its completion point. This method relies on observing the change in pH or another indicator to identify the equivalence point of the neutralization reaction, where stoichiometric amounts of acid and base have reacted.

Strong Acid and Strong Base Reaction

In titrations involving a strong acid and a strong base, both reactants dissociate completely in water, leading to a straightforward stoichiometric neutralization reaction. This complete dissociation means that the pH calculations are primarily based on the initial concentration of the acid or base before titration and the volumes mixed during the titration, with typical neutral solutions forming at the equivalence point.