What volume (in milliliters) of 0.100 M NaOH should be added to a 0.120 L solution of 0.024 M glycine hydrochloride (pKa1 = 2.350, pKa2 = 9.778) to adjust the pH to 2.95?
I don't know how to do this problem! Steps with answers please!! HELP!!
To solve this problem, we will use the Henderson-Hasselbalch equation, which relates the pH of a solution to the pKa and the ratio of the concentrations of the acid and its conjugate base. In this case, the acid is glycine hydrochloride (H2A) and its conjugate base is glycine (A-).
Here are the steps to find the volume of NaOH needed:
Step 1: Convert the pH to the corresponding H+ concentration.
The pH is given as 2.95. To convert it to [H+], we can use the equation: [H+] = 10^(-pH). Therefore, [H+] = 10^(-2.95).
Step 2: Calculate the ratio of [A-]/[H2A].
The Henderson-Hasselbalch equation is: pH = pKa + log([A-]/[H2A])
Given that pKa1 = 2.350, we can set up the equation as follows: 2.95 = 2.350 + log([A-]/[H2A])
Step 3: Solve for the ratio of [A-]/[H2A].
Rearrange the equation from step 2 and solve for [A-]/[H2A]. [A-]/[H2A] = 10^(pH - pKa1).
Step 4: Calculate the concentration of H2A.
The concentration of H2A is given as 0.024 M in a 0.120 L solution. Therefore, the moles of H2A are calculated as: moles of H2A = concentration of H2A * volume of solution
Step 5: Calculate the concentration of A-.
The concentration of A- can be found by multiplying the moles of H2A by the ratio of [A-]/[H2A] calculated in step 3.
Step 6: Calculate the moles of NaOH needed.
Since NaOH is a strong base, it completely dissociates to Na+ and OH-. Therefore, the moles of OH- needed is the same as the moles of A- calculated in step 5.
Step 7: Calculate the volume of NaOH needed.
The concentration of NaOH is given as 0.100 M. Therefore, the volume of NaOH needed is calculated as: volume of NaOH = moles of NaOH / concentration of NaOH
Follow these steps, and you will find the volume of NaOH needed to adjust the pH to 2.95.