Chapter 5

What is the oxidation number of sulfur in the tetrathionate ion, \(\mathrm{S}_{4} \mathrm{O}_{6}^{2-} ?\)

In Practice Exercise 5.6 (Section 5.1), some of the uses of chlorine dioxide were described along with a reaction that could be used to make \(\mathrm{ClO}_{2}\). Another reaction that is used to make this substance is \(\mathrm{HCl}+\mathrm{NaOCl}+2 \mathrm{NaClO}_{2} \longrightarrow 2 \mathrm{ClO}_{2}+2 \mathrm{NaCl}+\mathrm{NaOH}\) Which element is oxidized? Which element is reduced? Which substance is the oxidizing agent and which is the reducing agent?

What is the average oxidation number of carbon in (a) \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\) (grain alcohol), (b) \(\mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}\) (sucrose, table sugar), (c) \(\mathrm{CaCO}_{3}\) (limestone), and (d) \(\mathrm{NaHCO}_{3}\) (baking soda)?

In each of the following pairs, choose the metal that would most likely react more rapidly with a nonoxidizing acid such as HCl: (a) aluminum or iron, (b) zinc or nickel, and (c) cadmium or magnesium.

A solution contains \(\mathrm{Ce}\left(\mathrm{SO}_{4}\right)_{3}^{2-}\) at a concentration of \(0.0150 \mathrm{M}\). It was found that in a titration, \(25.00 \mathrm{~mL}\) of this solution reacted completely with \(23.44 \mathrm{~mL}\) of 0.032 \(M \mathrm{FeSO}_{4}\) solution. The reaction gave \(\mathrm{Fe}^{3+}\) as a product in the solution. In this reaction, what is the final oxidation state of the Ce?

A copper bar with a mass of \(12.340 \mathrm{~g}\) is dipped into \(255 \mathrm{~mL}\) of \(0.125 \mathrm{M} \mathrm{AgNO}_{3}\) solution. When the reaction that occurs has finally ceased, what will be the mass of unreacted copper in the bar? If all the silver that forms adheres to the copper bar, what will be the total mass of the bar after the reaction?

The ion OSCN \(^{-}\) is found in human saliva. Discuss the problems in assigning oxidation numbers to the atoms in this ion. Suggest a reasonable set of oxidation numbers for the atoms in OSCN \(^{-}\).

Assuming that a chemical reaction with DNA could lead to damage causing cancer, would a very strong or a weak oxidizing agent have a better chance of being a carcinogen? Justify your answer.

Do we live in an oxidizing or reducing environment? What effect might our environment have on chemistry we do in the laboratory? What effect might the environment have on the nature of the chemicals (minerals, etc.) we find on earth?