A 70.0 mL solution of 0.171 M potassium alaninate (H2NC2H5CO2K) is titrated with 0.171 M HCl. The pKa values for the amino acid alanine are 2.344 (pKa1) and 9.868 (pKa2), which correspond to the carboxylic acid and amino groups, respectively.

a) Calculate the pH at the first equivalence point.
b) Calculate the pH at the second equivalence point.

HELP! I don't know what to do, i need the steps and answers please

To calculate the pH at the first equivalence point, we need the volume of the acid solution required to reach the equivalence point. We know that the concentration of both the potassium alaninate solution and the HCl solution is 0.171 M.

The first equivalence point occurs when the moles of HCl added are equal to the moles of potassium alaninate in the solution. The number of moles of HCl can be calculated using the equation:

moles of HCl = concentration of HCl × volume of HCl used (in liters)

Since the concentration of HCl is 0.171 M, we can substitute this value into the equation.

Now, we need to find the volume of HCl required to reach the first equivalence point. To do this, consider the reaction between HCl and potassium alaninate:

H2NC2H5CO2K + HCl → H2NC2H5CO2H + KCl

The balanced equation tells us that 1 mole of HCl reacts with 1 mole of potassium alaninate. Therefore, the volume of HCl required to reach the first equivalence point will be the same as the volume of potassium alaninate solution used.

Given that the volume of the potassium alaninate solution is 70.0 mL (0.070 L), and knowing the concentration of HCl and the volume used, we can calculate the moles of HCl added.

After determining the moles of HCl, we can calculate the moles of potassium alaninate that reacted with the HCl. Since the potassium alaninate is a strong base, we can assume that all of it reacts with the HCl, resulting in a neutralization reaction.

Knowing the initial moles of potassium alaninate and the moles that reacted with the HCl, we can determine the remaining moles of potassium alaninate.

Finally, we can use the Henderson-Hasselbalch equation to calculate the pH. The Henderson-Hasselbalch equation is given by:

pH = pKa + log([A-]/[HA])

For the first equivalence point, consider the first dissociation of alanine. The pKa1 value is 2.344, and the ratio [A-]/[HA] is determined by the moles of alanine remaining and the volume of the solution.

After calculating this ratio, substitute the values into the Henderson-Hasselbalch equation to find the pH at the first equivalence point.

To calculate the pH at the second equivalence point, we will follow similar steps. In this case, we are considering the second dissociation of alanine. The pKa2 value is 9.868, and the ratio [A-]/[HA] is again determined by the moles of alanine remaining and the volume of the solution.

After calculating this ratio, substitute the values into the Henderson-Hasselbalch equation to find the pH at the second equivalence point.

By following these steps and employing the Henderson-Hasselbalch equation, you should be able to calculate the pH at both the first and second equivalence points.