Consider some of the precautions that must be taken when conducting single-molecule spectroscopy experiments.

(a) What is the molar concentration of a solution in which there is, on average, one solute molecule in 1.0 m3 (1.0 £1) of solution?

(b) It is important to use pure solvents in single-molecule spectroscopy because optical signals from fluorescent impurities in the solvent may mask optical signals from the solute. Suppose that water containing a fluorescent impurity of molar mass 100 g mol-1 is used as solvent and that analysis indicates the presence of 0.10 mg of impurity per 1.0 kg of solvent. On average, how many impurity molecules will be present in 1.0 μm of solution? You may take the density of water as 1.0 g cm-3, Comment on the suitability of this solvent for single-molecule spectroscopy experiments.