Question

How much of 0.3 M ammonium hydroxide should be mixed with 30 mL of 0.2 M solution of ammonium chloride to give buffer solution of pH 8.65 and 10? ($pK_{b}$ = 4.75)

Answer 1

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Answer 2

Answer:

Explanation:

Let V mL of NH4OH be mixed with NH4CI to have a buffer of pH 8.65. The total volume after mixing becomes (V+ 30) mL.

m Mole of NH4OH = 0.3×V

Thus, NH4OH = 0.3×V/ (v+30)

m Mole of NH4CL = 0.2×30

Thus, NH4CL  = 0.2×30/ (v+30)

= 0.2×30/ (v+30)/ 0.3×V/ (v+30)

= 0.61 = log6 /0.3×V

= v = 4.91mL

Similarly,

14-10 = 4.74+log 0.2×30/ (v+30)/ 0.3×V/ (v+30)

for ph = 10

V = 109.9mL