Question

3. 10 points total. Consider the buffer solution that can be created from the weak acid, HF and its conjugate base a. Write the balanced equilibrium equation for this buffer solution. (5 points) b. Applying Le Chatlier's principle, predict which way equilibrium shift with the following disturbances: (1 point each) i. Add hydroxide ii. Remove hydronium iii. Add hydronium c. If 2.5 mol of HF is used to make the buffer solution, how much of the conjugate base (in moles) should be added? (2 points)

Answer 1

3. a) The balanced cekleri equilibrium equation for buffer solution of ه م را acid u F S ins salt HIF + H2O H2 O+ + + fi by it IS IS are add hydroxidre (oHe then it reacts with hy dronium ion (H3ot) 10 prodnce water: H₂ot + 01 2 H20 H30+ so, Concentration of decreases Concentration of H2O increases So, according to Le-chattelier principle to maintain equilibrium , the above equilibrium i must be shift to the right (or forward) direction). remove H3ot Remove H30+; if we then to maintain equilibrium, the equilibrium (1) must shift to right (or forcoord direction). > Add Add Hydronium: If we add hydroni (H307) the Concentration of increases, so to maintain equilibrium , the above must shift left (or backword direction). Hoot equibrium (6) to c) we know when Concentration of of weak acid its salt equal then buffer Capacity (or activity of a buffer) ist maximum. so, if 2.5 HF is ured then Obviously 2.5 moles Conjugate bare (salt) is added. mole