For each solution, calculate the initial and final pH after adding 0.010 mol of NaOH. a. 250.0 mL of pure water b. 250.0 mL of a buffer solution that is 0.195 M in HCHO₂ and 0.275 M in KCHO₂ c. 250.0 mL of a buffer solution that is 0.255 M in CH₃CH₂NH₂ and 0.235 M in CH₃CH₂NH₃Cl

Verified step by step guidance

1. Step 1: Identify the acid and base in the buffer solution. In this case, CH3CH2NH2 is the base and CH3CH2NH3Cl is the acid. The NaOH will react with the acid component of the buffer.
2. Step 2: Calculate the initial pH of the buffer solution using the Henderson-Hasselbalch equation: pH = pKa + log([base]/[acid]). The pKa can be found by taking the negative logarithm of the Ka of the acid, which can be found in a table of acid dissociation constants.
3. Step 3: Calculate the moles of the acid and base in the buffer solution. This can be done by multiplying the molarity of each by the volume of the solution in liters.
4. Step 4: Calculate the moles of NaOH added and subtract this from the moles of the acid in the buffer. This is because the NaOH will react with the acid, reducing its amount. Add the moles of NaOH to the moles of the base, as the reaction produces more base.
5. Step 5: Calculate the final pH of the buffer solution using the Henderson-Hasselbalch equation again, but this time with the new amounts of acid and base.

Key Concepts

Buffer Solutions

A buffer solution is a system that resists changes in pH upon the addition of small amounts of acid or base. It typically consists of a weak acid and its conjugate base or a weak base and its conjugate acid. In this case, the buffer is made from the weak base CH3CH2NH2 and its conjugate acid CH3CH2NH3Cl, which helps maintain a relatively stable pH when NaOH is added.

Henderson-Hasselbalch Equation

The Henderson-Hasselbalch equation is a mathematical formula used to calculate the pH of a buffer solution. It is expressed as pH = pKa + log([A-]/[HA]), where [A-] is the concentration of the base and [HA] is the concentration of the acid. This equation is essential for determining the initial and final pH of the buffer after the addition of NaOH, as it allows for the quantification of the ratio of the base and acid components.

Neutralization Reaction

A neutralization reaction occurs when an acid reacts with a base to form water and a salt, resulting in a change in pH. In this scenario, the addition of NaOH, a strong base, will react with the weak acid component of the buffer, CH3CH2NH3Cl, leading to a decrease in the concentration of the acid and an increase in the concentration of the base. Understanding this reaction is crucial for calculating the final pH of the buffer solution.