You are given sodium acetate, 1M HCl, NaHCO3 and Na2CO3. Determine which of thes

Question

You are given sodium acetate, 1M HCl, NaHCO3 and Na2CO3. Determine which of these four you would need and then show calculations to make buffer pH = 4.7 by method 2. Assume making 100 mls of a 0.1 M buffer.

Neutralization of a portion of the weak base with sufficient strong acid to give the desired ratio, [A- ]/[HA]: Na+ + A- + HCl HA + Na+ + Cl-

I've been having a lot of trouble going step by step with this one. If you could really explain the logic behind each step it would be very much appreciated!! I'm also confused about the ka value. Am I just supposed to look that up? Thank you so much for your time!

Explanation / Answer

Here, given that the pH of the buffer = 4.7

Now,

pKa of bicarbonate = 6.37

pKA of acetic acid = 4.7

Therefore, we will use this acid and its salt

Again, we are provided with salt already

So, we need to find out the concentration of acid required

Now -

pH = pKa + log [Salt] / [acid]

4.7 = 4.7 + log [salt/[acid]

Further, concentration of acid and salt should be same

So, concentration of sodium acetate = 0.05 = [Acetic acid]

Again, volume = 100 mL

Moles = 0.005 moles of each

We will take 0.05M of 50mL sodium acetate and will react it with 50mL of 0.05 M of HCl

CH3COONa + HCl CH3COOH + NaCl

Therefore, the requisite solution combine 50mL of above solution with 50mL of 0.05 M of sodium acetate.

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