How do you calculate the PH of a buffer solution prepared by mixing 75 mL of 1.0 M lactic acid and 25 mL of 1.0 M sodium lactate?

(acid) = 1M x 75/100 = ??

(salt) = 1 M x 25/100 = ??
Plug into the Henderson-Hasselbalch equation.

4.34

Calculating pH can be quite a "sour" subject, but fear not, my friend! I'll do my best to guide you through this pickle of a problem.

To tackle this, we'll need to remember the Henderson-Hasselbalch equation, which is as follows:

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

Where:
pH = the pH of the buffer solution
pKa = the acid dissociation constant of lactic acid
[A-] = concentration of the conjugate base (in this case, sodium lactate)
[HA] = concentration of the acid (in this case, lactic acid)

Now, let's break it down:

First, we need to find the pKa value for lactic acid. The pKa for lactic acid is approximately 3.86. Nice!

Next, let's determine the concentrations of sodium lactate and lactic acid:

Concentration of sodium lactate ([A-]) = (25 mL / 1000 mL) * 1.0 M = 0.025 M

Concentration of lactic acid ([HA]) = (75 mL / 1000 mL) * 1.0 M = 0.075 M

Now, let's plug it all into the Henderson-Hasselbalch equation:

pH = 3.86 + log(0.025/0.075)

By calculating this equation, you'll find the pH of the buffer solution. Remember, a good sense of humor helps when dealing with chemistry, so keep those lab goggles on and give it a shot!

To calculate the pH of a buffer solution, you need to consider the dissociation of the acidic and its conjugate base components of the buffer. In this case, lactic acid (CH3CH(OH)COOH) is the acidic component, and sodium lactate (CH3CH(OH)COONa) is the conjugate base.

1. First, calculate the moles of lactic acid and sodium lactate in the solution:
- Moles of lactic acid = volume (in L) × concentration (in M)
Moles of lactic acid = 0.075 L × 1.0 M = 0.075 moles
- Moles of sodium lactate = volume (in L) × concentration (in M)
Moles of sodium lactate = 0.025 L × 1.0 M = 0.025 moles

2. Next, determine the number of moles of lactic acid that have dissociated into H+ ions. For a weak acid like lactic acid, you assume partial dissociation. So, you need to use the acid dissociation constant (Ka) to find the concentration of H+ ions:
Ka = [H+][CH3CH(OH)COO-] / [CH3CH(OH)COOH]
Assuming partial dissociation, we can assume that [CH3CH(OH)COO-] ≈ [H+]
Therefore, Ka = [H+]^2 / [CH3CH(OH)COOH]
Rearranging, [H+] = sqrt(Ka × [CH3CH(OH)COOH])
Here, the value of Ka for lactic acid is 1.4 × 10^-4

[H+] = sqrt((1.4 × 10^-4) × 0.075 moles)
[H+] ≈ 0.00139 M

3. Now, calculate the concentration of OH- ions using the Kw, which is the ion product of water:
Kw = [H+][OH-]
At room temperature (25 degrees Celsius), Kw is approximately 1.0 x 10^-14.
Therefore, [OH-] = Kw / [H+]
[OH-] = (1.0 x 10^-14) / (0.00139 M)
[OH-] ≈ 7.19 x 10^-12 M

4. Since it is a buffer solution, the pH is calculated using the equation:
pH = pKa + log([A-] / [HA])
where pKa = -log(Ka), [A-] is the concentration of the conjugate base, and [HA] is the concentration of the acid. In this case, [A-] = [CH3CH(OH)COO-] = 0.025 moles and [HA] = [CH3CH(OH)COOH] = 0.075 moles.

pH = -log(1.4 × 10^-4) + log(0.025 / 0.075)
pH ≈ -1.85 + log(0.333)
pH ≈ -1.85 + (-0.477)
pH ≈ -2.327

Therefore, the pH of the buffer solution obtained by mixing 75 mL of 1.0 M lactic acid and 25 mL of 1.0 M sodium lactate is approximately -2.327.

the pKa of lactic acid is 3.86

pH=3.86+ log[(25x1.0)÷(75x1.0-3)]

pH = 3.38

the pKa of sodium lactate 3.78

pH=3.78+ log[(25x1.0)÷(75x1.0-3)]

pH = 3.30