Physical chemistry - 7. Equilibria

Content

I - Chemical equilibria: reversible reactions; dynamic equilibrium

II - Ionic equilibria

Learning outcomes

Candidates should be able to:

(a) *explain, in terms of rates of the forward and reverse reactions, what is meant by a reversible reaction and dynamic equilibrium

(b) *state Le Chatelier’s Principle and apply it to deduce qualitatively (from appropriate information) the effects of changes in temperature, concentration or pressure, on a system at equilibrium

(c) deduce whether changes in concentration, pressure or temperature or the presence of a catalyst affect the value of the equilibrium constant for a reaction

(d) deduce expressions for equilibrium constants in terms of concentrations, Kc, and partial pressures, Kp [treatment of the relationship between Kp and Kc is not required]

(e) calculate the values of equilibrium constants in terms of concentrations or partial pressures from appropriate data

(f) calculate the quantities present at equilibrium, given appropriate data (such calculations will not require the solving of quadratic equations)

(g) describe and explain the conditions used in the Haber process and the Contact process, as examples of the importance of an understanding of chemical equilibrium in the chemical industry (see also Section 9.6)

(h) show understanding of, and use the Brønsted-Lowry theory of acids and bases

(i) explain qualitatively the differences in behaviour between strong and weak acids and bases and the pH values of their aqueous solutions in terms of the extent of dissociation

(j) explain the terms pH, Ka, pKa, Kw and use them in calculations

(k) calculate [H+(aq)] and pH values for strong and weak acids and strong bases

(l) explain the choice of suitable indicators for acid-base titrations, given appropriate data

(m) *describe the changes in pH during acid-base titrations and explain these changes in terms of the strengths of the acids and bases

(n) Buffers

(o) calculate the pH of buffer solutions, given appropriate data

(p) show understanding of, and use, the concept of solubility product, Ksp

(q) calculate Ksp from concentrations and vice versa

(r) show understanding of the common ion effect