1)A buffer solution that is 0.10 M sodium acetate and 0.20 M acetic acid is prepared. Calculate the initial pH of this solution.
The Ka for CH3COOH is 1.8 x 10-5 M. As usual, report pH to 2 decimal places.
*A buffered solution resists a change in pH.*
2)Calculate the pH when 28.8 mL of 0.035 M HCl is added to 100.0 mL of the above buffer.
3)Calculate how many mL of 0.100 M NaOH are needed to neutralize completely 55.0 mL of 0.0900 M HCl.
4)Calculate how many mL of 0.100 M NaOH are needed to neutralize completely 86.0 mL of 0.0400 M H2SO4 (forming Na2SO4 and water).
5)Calculate how many mL of 0.100 M NaOH are needed to neutralize completely 62.0 mL of 0.0600 M acetic acid.
For 1 use the Henderson-Hasselbalch equation to calculate pH.
2. Set up an ICE chart. The I line is what you start with in problem 1, the C line is what you're adding from problem 2, the E line is to be calculated and plugged into the HH equation and solve for the new pH.
3,4,5. mols acid = M x L
Convert mols acid to mols NaOH.
M NaOH = mols NaOH/L NaOH. You will have M and mols, solve for L and convert to mL.
Post your work if you get stuck.
To solve these questions, we need to understand some basic concepts of acid-base chemistry and buffers. Let's break down each question and explain the steps to find the answers.
1) The initial pH of a buffer solution can be calculated using the Henderson-Hasselbalch equation: pH = pKa + log ([A-]/[HA]).
Here, pKa is the negative logarithm of the acid dissociation constant (Ka), [A-] is the concentration of the conjugate base (acetate), and [HA] is the concentration of the acid (acetic acid).
In this case, the given concentrations are [A-] = 0.10 M and [HA] = 0.20 M. The Ka for acetic acid (CH3COOH) is 1.8 x 10^-5 M.
So, first, calculate the pKa: pKa = -log (Ka) = -log (1.8 x 10^-5).
Then, use the Henderson-Hasselbalch equation to find the pH: pH = pKa + log ([A-]/[HA]).
Substitute the known values: pH = pKa + log (0.10/0.20). Calculate the pH using a calculator.
2) When HCl is added to the buffer, it reacts with the acetic acid in the buffer to form its conjugate base (acetate) and water. The amount of HCl added affects the concentration of the acetic acid and acetate in the buffer.
To calculate the new pH, we need to determine the new concentrations of acetic acid and acetate after the addition of HCl.
Given volumes: V1 = 28.8 mL (HCl), V2 = 100.0 mL (buffer).
Given concentrations: C1 = 0.035 M (HCl), C2 = initial concentrations of the buffer components.
Since the volume is constant, we can use the equation C1V1 = C2V2 to find the new concentrations.
First, use C1V1 = C2V2 to calculate the new concentration of acetic acid (HA).
Then, calculate the new concentration of acetate (A-) using the equation [HA] + [A-] = initial concentration of the buffer components.
Finally, use the Henderson-Hasselbalch equation with the new concentrations of the buffer components to find the new pH.
3) To determine the volume of NaOH needed to neutralize the HCl completely, we can use the equation: M1V1 = M2V2.
Given volumes: V1 = 55.0 mL (HCl), V2 = unknown volume of NaOH required.
Given concentrations: C1 = 0.0900 M (HCl), C2 = 0.100 M (NaOH).
Substitute the known values into the equation and solve for V2.
4) Similar to question 3, to neutralize sulfuric acid (H2SO4) with NaOH, we can use the equation: M1V1 = M2V2.
Given volumes: V1 = 86.0 mL (H2SO4), V2 = unknown volume of NaOH required.
Given concentrations: C1 = 0.0400 M (H2SO4), C2 = 0.100 M (NaOH).
Substitute the known values into the equation and solve for V2.
5) To neutralize acetic acid (CH3COOH) with NaOH, we can use the same equation: M1V1 = M2V2.
Given volumes: V1 = 62.0 mL (acetic acid), V2 = unknown volume of NaOH required.
Given concentrations: C1 = 0.0600 M (acetic acid), C2 = 0.100 M (NaOH).
Substitute the known values into the equation and solve for V2.
Remember to pay attention to the stoichiometry of the reaction and consider the balanced equation when using these formulas.