Show Calculations used in mkaing 250mL of 0.5M sodium acetate ph 4.7.
You are given:
1M acetic acid (weak acid)
1M sodium hydroxide (strong base)
Sodium acetate buffer: ph 4.7
acetic acid pKa: 4.7
So far this is what I've gotten:
pH = pKa + log (A-/HA-)
4.7=4.7 + log (A-/HA-)
0 = log (A-/HA-)
(A-/HA-) = 1
A- = HA -
0.5M x 0.25L = 0.125 moles of each to 250 mL of water.
Not sure if correct.
Thank you!
To make a 250 mL solution of 0.5M sodium acetate at pH 4.7, you need to follow these steps:
Step 1: Determine the moles of sodium acetate required:
Given that the desired concentration is 0.5M and the volume is 250 mL, you can use the formula:
moles = concentration (M) x volume (L)
moles = 0.5 M x 0.25 L = 0.125 moles
So, you need 0.125 moles of sodium acetate.
Step 2: Calculate the moles of acetic acid required:
Since the acid and conjugate base are in a 1:1 ratio for this buffer system, the moles of acetic acid required will also be 0.125 moles.
Step 3: Calculate the volume of acetic acid and sodium hydroxide solutions needed:
To calculate the volume of 1M acetic acid (HA) needed, you can use the formula:
volume (L) = moles / concentration (M)
volume (L) = 0.125 moles / 1 M = 0.125 L = 125 mL
So, you need 125 mL of 1M acetic acid.
Next, the volume of 1M sodium hydroxide (A-) needed will also be 125 mL since they are in a 1:1 ratio.
Step 4: Combine the solutions:
Combine the 125 mL of 1M acetic acid (HA) and 125 mL of 1M sodium hydroxide (A-) in a 250 mL container.
This will result in a solution containing 0.5M sodium acetate at a pH of 4.7, which is a sodium acetate buffer solution.
Please note that when working with strong acids or bases (e.g., sodium hydroxide), it is essential to take safety precautions and handle these corrosive substances carefully.
To make 250mL of 0.5M sodium acetate pH 4.7, you need to follow these steps:
Step 1: Calculate the amount of acetic acid (HA) needed
Since the pKa of acetic acid is 4.7, and you want a buffer at pH 4.7, the concentration of the acid (HA) and its conjugate base (A-) should be equal. Therefore, you need 0.5 moles of acetic acid (HA) for every liter (1000mL) of the buffer.
Amount of acetic acid (HA) needed = 0.5 moles/L x 0.25 L = 0.125 moles
Step 2: Calculate the amount of sodium hydroxide (NaOH) needed
To convert the acetic acid into its conjugate base (sodium acetate), you need to add an equivalent amount of sodium hydroxide (strong base). Sodium hydroxide has a 1:1 stoichiometric ratio with acetic acid.
Amount of sodium hydroxide (NaOH) needed = 0.125 moles
Step 3: Prepare the buffer solution
a) Dissolve 0.125 moles of acetic acid (HA) in a small volume of water (less than 250mL).
b) Add 0.125 moles of sodium hydroxide (NaOH) to the same container.
c) Transfer the solution to a 250mL volumetric flask.
d) Fill the flask to the mark with water, ensuring a final volume of exactly 250mL.
By following these steps, you will have prepared a 250mL solution of 0.5M sodium acetate with a pH of 4.7.