Chemical Equilibria


Chromate-Dichromate Equilibrium – Show the pH dependence of the CrO42-/Cr2O72- system.

Cobalt Complexes and Temperature v2.0 – Demonstrate effects of concentration and temperature changes on the Co(H2O)62+/CoCl42- equilibrium.

Common Ion Effect Demos

  • Acetic Acid and Sodium Acetate – Add NaCH3COO to a solution of acetic acid and indicator; the color change accompanying the change in pH shows the equilibrium shift caused by the common ion effect.
  • HCl and NaCl – Add concentrated HCl (aq) to saturated NaCl (aq) to cause precipitation of NaCl (s).
  • Mg(OH)2 – Mix 1 M MgCl2 (aq) and 1 M NH3 (aq) to form Mg(OH)2 (s). Add NH4Cl (s) and NH4+ removes OH to reform NH3, so Mg(OH)2 dissolves to replace OH.

Complex Ion Formation- Nickel and Copper  – In a tall graduated cylinder – carefully add 6 M NH(aq) to 1 M CuSO4 (aq) (or NiNO3) to obtain a layering effect with the Cu2+ (aq), Cu(OH)2 (s), and Cu(NH3)42+ (aq).

Effect of Pressure on the Melting Point of Ice – Hang a wire weighted at both ends over a cylinder of ice; eventually the wire passes through the ice and the weights fall, leaving the ice intact. The ice below the wire melts due to pressure from the weights, and the water above the wire refreezes as the pressure is relieved.

LeChatelier’s Principle – Iron(III) Thiocyanate – Apply stress to the Fe3+ + SCN → FeSCN2+ system in five different ways to show the equilibrium shifts accompanying changes in the concentration of reactants.