Question

A buffer solution is able to maintain a constant pH when small amounts of acid or base are added to the buffer. Consider what happens when 1 mL of a 5 M solution is added or 0.005 mol of HCl are added to a 100.0 mL solution acetic acid buffer that contains 0.0100 mol of Acetic acid, HC,H,O,, and 0.0100 mol of sodium acetate, NaC,H,O,. The initial concentration of both the acid and the base are 0.0100 mol/ 0.1000 L = 0.100 M; therefore, according to the Henderson-Hasselbach equation, log(x) = log 1 = 0 log(a) = log1 = 0 and the pH = pK, = 4.75. The reaction is HC,H,O, +1,0 H,0* + C,H,O,: The HCl added will react with the conjugate base, removing it producing more of the weak acid. The reaction shifts to remove the added acid and will return to equilibrium. We can determine the amounts of each species if we look at the moles stoichiometrically and then use the ICE table to determine the equilibrium concentrations. HC,H,O2 = H,O* + CH,0, The species in the acid reaction Initial moles This is the amount of each species before acid 0.0100 0.0100 present added Molarity x Volume (L) = moles of solute Mole of H When the acid is added it increases added the concentration of product, the 0.005 reaction will shift to remove what was added by reacting with the conjugate base and producing more weak acid Change due This shows that the acid is removed to added acid +0.005 -0.005 -0.005 initially, reacting with the conjugate base and the amount of weak base increases by the same O 3 | Page

Answer 1

1) a) HNO2 :ui trous auid Ka = +1 xlo Sodium Aalt NaNo (sodium ncbute) b HF: Hydmopluowc auid Ka 7-2xlo Sodium Pluorids NaF H Poy: Phosphoic auid Ka, 7-5 xi 3 NaH2 Poy, Na, Hpa Na3Poy 3-5odium Satts kar 6-2 x168 Ka3=4.8 xlo13 2.aNHS b) ChNH - NHyci (Ammowum uchlende CNH C Methylammonium chloride