Redox I: Practice Questions

In which of the following compounds does oxygen exhibit an oxidation number of \(-1\)?

In the reaction between concentrated nitric acid and copper, the unbalanced equation is:
\(Cu + H^+ + NO_3^- \rightarrow Cu^{2+} + NO_2 + H_2O\)
By constructing half-equations, determine the coefficient of \(H^+\) in the balanced ionic equation.

Which statement best describes a disproportionation reaction?

A sample of \(VO^{2+}\) ions is reacted with a reducing agent. If \(1.50 \times 10^{-3}\) mol of \(VO^{2+}\) requires \(3.00 \times 10^{-3}\) mol of electrons for complete reduction, what is the final oxidation state of vanadium?

What are the oxidation numbers of sulfur in \(Na_2S_2O_3\) and \(Na_2S_4O_6\) respectively? (Assume the average oxidation state for the tetrathionate ion)

In the reaction between magnesium and steam, identify the changes in oxidation number for the elements involved and state which species is the reducing agent.
\( Mg(s) + H_2O(g) \rightarrow MgO(s) + H_2(g) \)

The disproportionation of chlorine in hot concentrated sodium hydroxide solution follows the equation:
\( 3Cl_2 + 6NaOH \rightarrow 5NaCl + NaClO_3 + 3H_2O \)
Show by calculation of oxidation numbers that this is a disproportionation reaction.

Calculate the oxidation number of the sulfur atom in the peroxodisulfate ion, \( S_2O_8^{2-} \), given that the structure contains a peroxide (\( -O-O- \)) linkage.

Chlorine reacts with cold, dilute aqueous sodium hydroxide in a disproportionation reaction.
(a) Write the full balanced equation for this reaction, including state symbols.
(b) Using oxidation numbers, explain why this is classified as a disproportionation reaction.
(c) Predict how the products would differ if hot, concentrated sodium hydroxide were used instead of cold, dilute sodium hydroxide. Provide the oxidation number of chlorine in the new chlorine-containing product.

The reaction between copper and nitric acid depends on the concentration of the acid. With concentrated nitric acid, nitrogen dioxide (\( NO_2 \)) is produced. With dilute nitric acid, nitrogen monoxide (\( NO \)) is produced.
(a) Calculate the oxidation number of nitrogen in \( HNO_3 \), \( NO_2 \), and \( NO \).
(b) Write the ionic half-equation for the reduction of dilute \( HNO_3 \) to \( NO \).
(c) Use the half-equation for the oxidation of copper to \( Cu^{2+} \) and your answer to (b) to construct the full ionic equation for the reaction of copper with dilute nitric acid.