Sketch titration curves for the following acid-base titrations: (a) \(\mathrm{HCl}\) versus \(\mathrm{NaOH},\) (b) \(\mathrm{HCl}\) versus \(\mathrm{CH}_{3} \mathrm{NH}_{2},\) (c) \(\mathrm{CH}_{3} \mathrm{COOH}\) versus \(\mathrm{NaOH}\). In each case, the base is added to the acid in an Erlenmeyer flask. Your graphs should show \(\mathrm{pH}\) on the \(y\) axis and volume of base added on the \(x\) axis.

Acid-Base Titration is a laboratory procedure used to determine the concentration of an acid or base in a solution. It involves the gradual addition of a solution of known concentration (the titrant) to a solution of unknown concentration (the analyte) until the reaction between the two is complete. This is visually represented by a color change in the solution or by reaching a certain pH level when a pH indicator is used.

In practical terms, imagine slowly adding drops of a base to an acid sitting in an Erlenmeyer flask. As you add the base, the acid in the flask reacts and the pH of the solution gradually changes. You can monitor these changes using a pH meter or an indicator that changes color at a specific pH value. The point of interest during titration is when the amount of added base exactly neutralizes the acid (or vice versa), which occurs at the equivalence point.

The titration process highlights key concepts such as the stoichiometry of the reaction, the role of indicators, and the interpretation of titration curves, which graphically represent the change in pH as the titrant is added. It is important to note that different combinations of acids and bases will produce different shapes of titration curves, reflecting their strength and dissociation in water.

The equivalence point in a titration is the moment where the amount of titrant added reacts exactly with the analyte present—essentially, moles of acid equal moles of base. For a strong acid-strong base titration, the equivalence point occurs at a pH of 7, illustrating that the solution is neutral. However, when a weak acid or base is involved, the pH at the equivalence point will be greater than 7 for weak acid-strong base titrations, or less than 7 for strong acid-weak base titrations, due to the incomplete dissociation of the weak reactant.

The identification of the equivalence point is crucial, as it allows chemists to calculate the concentration of the unknown solution. In many cases, a pH indicator is used, which changes color at a particular pH range, to signal the equivalence point visually. Experienced chemists can also use the titration curve itself to pinpoint the equivalence point, as it is indicated by a steep change in the pH. This sharp increase or decrease on the graph is known as the inflection point and is what the titration is designed to find, allowing the accurate determination of the analyte's concentration.

The pH level is a measure of the acidity or basicity of a solution, on a scale from 0 to 14. Solutions with a pH less than 7 are acidic, while those with a pH greater than 7 are basic (or alkaline). A pH of 7 indicates neutrality, which is typically the pH of pure water at 25°C (77°F).

pH levels in the context of titration curves represent how acidic or basic the solution is at each point of the titration process. The curve generally starts at the pH of the original acid or base solution, changes as the titrant is added, and notably shifts at the equivalence point. The final part of the titration curve reflects the pH of the excess titrant.

For example, when titrating a strong acid with a strong base, the pH level will start low (indicative of the strong acid), gradually rise through neutral pH as the solution becomes less acidic, and abruptly change at the equivalence point, continuing to rise as the base becomes the dominant component. Understanding pH levels is essential for predicting the outcome of a reaction and for interpreting titration curves during acid-base reactions.