What safety precautions should I take when demonstrating these changes?

Chromate(VI) and dichromate(VI) compounds are classified as suspected carcinogens/mutagens/tetragens and can cause skin irritation or allergic reactions. This demonstration uses very small quantities of diluted solutions and contact with the chemicals is avoided so no additional precautions should be necessary. However, if it were used as a class experiment the wearing of nitrile gloves might be sensible and good laboratory hygiene, such as washing hands at the end of the session, is essential.

How can I make sure that all of my students see the changes that occur?

You could carry out the demonstration using boiling tubes or even beakers. Alternatively, a visualiser or a camera linked to a projector could be used.

Could I use other equilibrium systems to illustrate the effect of changing concentration on equilibrium position?

Yes. You could use the equilibrium between Co(H₂O)₆²⁺ ions and CoCl₄^2– ions.

Alternatively, you could use the effect of acid and alkali on acid–base indicators such as methyl orange or bromothymol blue.