Question

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Worksheet 4. Which solution in above table has composition of an ideal buffer? The buffer in this experiment is made of acetic acid HCH.O and sodium acetate NaCHO. (CHO). Ka=1.76 x 10 for HCH:02 Each buffer composition is listed in the table below. 5. If the buffer is mainly used to neutralize added acid (H'), which buffer solution would be most effective? Please explain Test Tube Number Table 1 Solution Reference (Acetic acid) Buffer solution Buffer solution Buffer solution Reference (Sodium acetate) Control (Distilled water 6. If the buffer is mainly used to neutralize added acid (OH), which buffer solution would be most effective? Please explain. acetic acid, 0.1 M (ml.) sodium acetate, 0.1 M (ml) distilled water (mL.) 7. What would be effective buffer range for this buffer? 3. Calculate the pH of buffer solutions 2, 3 and 4

Answer 1

ka (CH3COOH) = 1.76x105 soln: - Acetic acid, o.im o sodium acetate , o. Im consugote Buffer solution A: Volume of acetic acid = 9 mL volume of sodium acetate base) = 3mL After mixing, concentration of [Acid] = 0.1 X 9 7 since both [consuget Base] = 0.1 3 same initial solution have 12 concentration. Explanation - Ta cid] = Number of moles of acid volume of solution. Here gmL of olm acid is taken, there -fore number of moles of acid present in this solution = molarity & volume a 0. 1xg After mixing volume of solution will be = 9+3=22mL similarly number of moles of salt I confugote base = 0.1 x3 thus [Acid] = o.lxg 12 concentration ratio will be similar to volume ratio. [Base] = 0.1 X 2 Ratio = [Base] = 3 = 1/3 [Acid] pH = pka + log (Bare py -- loy (11 76x105) + log (13) pH = 4.7544-0.4771 pH = 4:2773 ;.(pH = 4:28