Question

3. (a) Calculate the change in pH when 5.00 mL of 0.100 M HCl(aq) is added to 100.0 mL of a buffer solution that is 0.100 M in NH3(aq) and 0.100 M in NH4Cl(aq). (b) Calculate the change in pH when 5.00 mL of 0.100 M NaOH(aq) is added to the original buffer solution.

Answer 1

Finding initial phy butter Миа мек acid ми be рка 1 N441 - 4 26 Henderson Hasselbach equation pu= pk at log [conjugate base] acid P4 = 4-20 + lot (o 1) При е час б•1)

NHALL & NH₂ acid base DIM 0.1 ska og NHAT = 9.26 Volume of butter = loo oml Im = 0.0014 loomi = 0.IL md og NH3 = Molarity X Volume (l) - 0.1 oo mol xolk = 0.01 mol moly N144 = 0,1 mol Xolk - 0.0lmol x When He added present in butter of weak acid to this butter, to this butter, it it react with weak base rea and amount of weak base decrease and that increases. mol of Hu того, ч 0.005% X Olmol = 0.0005 mol и Afler addition mol q NH4Cl = 0.01 + 0.0005 = 0.010s moll mol 1 NH3 = 0.01 -0.0005 = 0.0095 mol pH of solution calculated as Hendersons Hasselbach equation ph= pka + log [base] Cacid = bka + log [N's) [N444] = 9.26 + log (0.0095) – 9.24 Tolos) change in ph= 19.26-9.22) = 0.04 unit pu decreases by orgy

added it react with acid and amount of acid Addition of Naoh when moly Naon decreases that of After addition base increases. = 0.0095 mol mol of acid = 0.01 -0.0005 moly base = 0.olt 0.0005 = 0.005 mol pH = prat log [ base] [acid] = 9.26+ log co.010s) (0.0015) pn = 9.30 Change in ph= 19.30-9.261 = 0.04 unit ph increase by 0.04