Question

if the reactant solution is used to write on a piece of paper and the paper is allowed to partially dry, what can be done to bring out the colored writing

Answer 1

Expose the paper to the atmosphere or moisture

Step-by-step explanation:

An interesting experiment that demonstrates the equilibrium of complexes is that of the invisible ink.

The invisible ink is pink colored [Co(H2O)6]Cl2 which is essentially colorless and pale when it is used to write on paper. This complex is almost colorless when dilute. Therefore, when it is used in writing, the writing can not be seen.

However, if the paper is left to stand or allowed to absorb moisture; the following equilibrium is set up:

[Co(H2O)6]Cl2 ⇄ [CoCl2(H2O)2] + 4H2O

The formation of blue [CoCl2(H2O)2] on standing or exposure to moisture enables the colored writing to be easily read.