{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

L18_AcidBase5_115b08

# L18_AcidBase5_115b08 - L18 pH of Salts Made of Acids and...

This preview shows pages 1–6. Sign up to view the full content.

? Weak Weak <7 Weak Strong >7 Strong Weak 7 Strong Strong Salt’s pH Base Acid L18: pH of Salts Made of Acids and Bases All equilibria are maintained simultaneously

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
What is the pH of a 0.1 M solution of NH 4 Cl? The K b of NH 3 = 1.8*10 -5 . Weak base NH 3 strong conjugate acid NH 4 + : NH 4 + ( aq ) + H 2 O( l ) NH 3 ( aq ) + H + ( aq ) – solution will be acidic (pH<7) K a = [NH 3 ] [H + ] [OH - ] = K w [NH 4 + ] [OH - ] K b Equilibrium: NH 4 + (aq) + H 2 O(l) NH 3 (aq) + H + (aq) Initial []: 0.1 0 0 Change: - x + x + x Equilibrium: 0.1- x x x K a = K w / K b = x 2 /0.1 = 1.0*10- 14 /1.8*10 -5 = 5.6*10 -10 x=7.5*10 -6 M=[H + ] pH = 5.13 (acidic) Notes: 1. x – small relative to 0.1M and large relative to 10 -7 2. In the solution all reactions take place at the same time.