1) say, for example, that you had prepared a Buffer C, in which you mixed 8.203g
ID: 967028 • Letter: 1
Question
1) say, for example, that you had prepared a Buffer C, in which you mixed 8.203g of sodium acetate, NaC2H3O2,with 100.0 mL of 1.0 M acetic acid.
1a) if you add 5.0 mL of 0.5M NaOH solution to 20.0 mL each of Buffer B and Buffer C, what would be the pH of Buffer B and C
1b) which buffers pH (from part a) changed less? explain
2) A buffer solution for a certain bacteria is needed for addition to some growth media. The bacteria has a narrow pH tolerance zone from 4.21-4.25 and produces acetic acid as a by-product of its metabolism. How would you prepare a 1L buffer solution for the bacteria using Sodium Acetate and Acetic Acid?
Explanation / Answer
1) No of mol of Sodium acetate = 8.203/82.0343 = 0.099 mol
No of mol of ACETICACID = 100/1000*1 = 0.1 mol
pKa = 4.74
pH = pka + log(salt/acid)
= 4.74 + log(0.099/0.1)
= 4.736
No of mol of NaOH added = 5/1000*0.5 = 0.0025 mol
pH = 4.74 + log((0.099 +0.0025)/(0.1-0.0025))
= 4.76
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