Solutes and Solutions

 

Cobalt and Nickel Ammine Complexes – Show the dependence of color on both the metal ion and its oxidation state by first adding concentrated NH(aq) to dilute solutions of Ni(NO3)2 and Co(NO3)2 and then adding part of the [Co(NH3)6](NO3)(aq) to a flask charged with O(g) to oxidize the Co2+ to Co3+ and show the accompanying color change.

Conductivity Tester Demos – Use two conductivity testers with light bulbs to contrast the conductivity of d-H2O, sugar solution, and salt solution.

Glittering Shower of Lead Iodide Crystals – Cool a hot colorless flask containing a solution of PbI(aq) to produce a glittering shower of yellow PbI(s) crystals.

Iodine Clock – Perform the iodine clock reaction with three different initial concentrations of IO3.

Lead Nitrate and Potassium Iodide: Solid and Liquid Reactions – Mix equal amounts of Pb(NO3)2 (s) and KI (s) in a test tube and shake thoroughly to show formation of yellow PbI2 (s). Contrast this with the results of mixing Pb(NO3)2 (aq) and KI (aq)

Like Dissolves Like – Contrast the solubility of I(s) and CuCl(s) in both water and hexane in large test tubes.

Miscibility vs Immiscibility – Mix ethanol and colored water in one beaker and hexane and colored water in another to demonstrate miscibility and immiscibility due to differences in the intermolecular forces of alcohols as the size of the alkyl group increases.  The demo can be repeated with octanol and water, to show that, as carbon chain length increases, polarity of alcohols decreases.

Osmotic Pressure – Small dialysis bags containing equimolar solutions of isopropanol and CaCl2 are attached to long glass tubes; immerse the bags in distilled water to illustrate osmosis and to show that osmotic pressure depends on the number of particles in solution.

Polarity and Solubility – Add acetone to a saturated solution of CuSO(aq) causing CuSO(s) to crystallize out – the solubility of CuSO4 decreases as the polarity of the solvent is decreased.

Precipitates and Complexes of Ni – Add different amounts of ethylenediamine to beakers of Ni2+ to contrast the colors of Ni(H2O)62+ and the Ni2+ chelate complexes with one, two, and three ethylenediamine molecules.

Precipitates and Complexes of Silver – Add a series of 7-9 reagents to Ag(aq) in succession to produce a series of precipitates and complexes.

Precipitation Reactions– CoCl2 + Na2CO3 vs. CoCl2 + Na2SO4 – mix two pairs of solutions to show that some combinations produce precipitate and some give no net reaction.

Solubility and Temperature – Heat two flasks, one containing saturated Ca(C2H3O2)2 and the other saturated KNO3; the calcium acetate will crystallize out and the potassium nitrate dissolves

Tyndall Effect– Demonstrate the Tyndall effect and simulate a sunset on the overhead projector by reacting Na2S2O3 with HCl to produce a colloidal suspension of sulfur.

Vapor Pressure- Solutions – Demonstrate the lower vapor pressure of solutions by knocking over a medicine cup of salt in a sealed manometer containing water.