“Green” chemistry methods, which use nontoxic chemicals, are replacing elemental chlorine for the bleaching of paper pulp. Chlorine causes problems because it is a strong oxidizing agent that reacts with organic compounds to form toxic byproducts such as furan and dioxins.

(a) Write the electron configuration of a chlorine atom in its ground state. How many unpaired electrons are present in the atom? Write the electron configuration you expect a chloride ion to have. The electron configuration of the chloride ion is identical to that of a neutral atom of what other element?

(b) When a chlorine atom is excited by heat or light, one of its valence electrons may be promoted to a higher energy level. Predict the most likely electron configuration for the lowest possible excited state for an excited chlorine atom.

(c) Estimate the wavelength (in nm) of the energy that needs to be absorbed for the electron to reach the excited state in part (b). To make this estimate, use Eq. 2 from Topic 1E and take the effective nuclear charge from Fig. 1F.3. (d) What is the value of the energy required in part (c) in kilojoules per mole and electronvolts?

(e) The proportion of ³⁷Cl in a typical sample is 75.77%, with the remainder being ³⁵Cl. What would the molar mass of a sample of chlorine atoms be if the proportion of ³⁷Cl were reduced to half its current value? The mass of an atom of ³⁵Cl is 5.807 * 10^-23 g and that of an atom of ³⁷Cl is 6.139 * 10^-23 g.

(f) What are the oxidation numbers of chlorine in the bleaching agents ClO₂ and NaClO?

(g) What are the oxidation numbers of chlorine in the oxidizing agents KClO₃ and NaClO₄?

(h) Write the names of the compounds in parts (f) and (g).

Transcribed Image Text:

Energy Before After Before After (a) Carbon FIGURE 1F.13 (b) Nitrogen