Chemistry Problem Solving: Determining the Volume of NaOH Required for Titration

How do we determine the volume of 0.149 M NaOH required to titrate to the equivalence point 20.0 mL of a 0.223 M solution of a monoprotic weak acid that is 26.0% ionized?

In this question, we are required to determine the volume of NaOH needed to titrate a specific volume and concentration of a monoprotic weak acid that is partially ionized at the equivalence point.

Answer:

The volume of 0.149 M NaOH required to titrate to the equivalence point 20.0 mL of a 0.223 M solution of a monoprotic weak acid that is 26.0% ionized is 30.0 mL.

In this particular chemistry problem, we are tasked with determining the volume of a specific concentration of NaOH needed to neutralize a monoprotic weak acid solution that is only partially ionized. The process involves calculating the moles of acid, considering the ionization percentage, and finally determining the volume of NaOH required for complete reaction.

To start, we need to write the balanced equation for the neutralization reaction: HA + NaOH → NaA + H₂O, where HA represents the weak acid and NaA is the salt formed.

Next, we calculate the number of moles of acid that react by using the formula Moles of Acid = Molarity × Volume. With the given concentration and volume of the weak acid solution, we find that 0.00446 mol of acid will react.

Since the acid is partially ionized at 26.0%, we must use the acid dissociation constant (Ka) expression to determine the hydronium ion concentration in solution. This step helps us find the concentration of hydronium ions, which is crucial for further calculations.

After determining the hydronium ion concentration, we calculate the moles of NaOH needed for the complete reaction, which turns out to be 0.00446 mol as well. Using this value, we can calculate the volume of NaOH required by dividing the moles of NaOH by its molarity, resulting in 0.0300 L or 30.0 mL.

Therefore, through a series of calculations involving moles, ionization percentage, and molarity, we can accurately determine the volume of 0.149 M NaOH needed to titrate the provided solution of a monoprotic weak acid to the equivalence point.