Oxidation numbers, redox reactions: แบบฝึกหัด

Arsenic(III) oxide ( \(\text{As}_2\text{O}_3\) ) reacts with acidified potassium dichromate ( \(\text{Cr}_2\text{O}_7^{2-}\) ) to produce arsenic acid ( \(\text{H}_3\text{AsO}_4\) ) and chromium(III) ions ( \(\text{Cr}^{3+}\) ). The unbalanced ionic equation for the reaction is:

\(\text{As}_2\text{O}_3(\text{s}) + \text{Cr}_2\text{O}_7^{2-}(\text{aq}) \rightarrow \text{H}_3\text{AsO}_4(\text{aq}) + \text{Cr}^{3+}(\text{aq})\)

When this equation is balanced using the smallest whole-number coefficients in acidic medium, what is the stoichiometric coefficient of water ( \(\text{H}_2\text{O}\) )?

Consider the reaction:
\( \text{H}_2\text{S}(\text{g}) + \text{I}_2(\text{aq}) \rightarrow 2\text{HI}(\text{aq}) + \text{S}(\text{s}) \)

Which species acts as the oxidizing agent?

Chlorine gas (\(Cl_2\)) is bubbled through hot concentrated aqueous potassium hydroxide (\(KOH\)) to produce chloride (\(Cl^-\)) and chlorate(V) (\(ClO_3^-\)) ions. After balancing the equation with the smallest whole number coefficients, what is the sum of the stoichiometric coefficients of the reactants (\(Cl_2\) and \(OH^-\))?

What is the oxidation number of chlorine in the chlorate ion, \( \text{ClO}_3^- \)?

In the reaction:
\( 3\text{Cu}(\text{s}) + 8\text{HNO}_3(\text{aq}) \rightarrow 3\text{Cu}(\text{NO}_3)_2(\text{aq}) + 2\text{NO}(\text{g}) + 4\text{H}_2\text{O}(\text{l}) \)

What is the change in the oxidation number of nitrogen?

Calculate the oxidation number of chlorine in the chlorite ion (\( \text{ClO}_2^{-} \)).

Consider the following reaction: \(\text{Sn}^{2+}\text{(aq)} + 2\text{Fe}^{3+}\text{(aq)} \rightarrow \text{Sn}^{4+}\text{(aq)} + 2\text{Fe}^{2+}\text{(aq)}\). Determine the change in oxidation number for tin and iron. Identify the oxidising agent and the reducing agent in this reaction.

When urea (\( \text{CO(NH}_2)_2 \)) reacts with nitrous acid (\( \text{HNO}_2 \)), the products are carbon dioxide, nitrogen gas, and water. Determine the oxidation number of nitrogen in both urea and nitrous acid, and find the mole ratio of \( \text{HNO}_2 \) to \( \text{CO(NH}_2)_2 \) in the balanced chemical equation.

Consider the reaction between aqueous sulfur dioxide and an acidified potassium dichromate(VI) solution.
(a) Determine the oxidation number of sulfur in \( \text{SO}_2 \).
(b) State the color change of the solution observed during the reaction.
(c) Identify the species that acts as the oxidizing agent in this reaction.

Consider the unbalanced reaction for the catalytic oxidation of ammonia:

$$\text{NH}_3(\text{g}) + \text{O}_2(\text{g}) \rightarrow \text{NO}(\text{g}) + \text{H}_2\text{O}(\text{l})$$

(a) Determine the oxidation number of nitrogen in $$\text{NH}_3$$ and $$\text{NO}$$.

(b) Determine the oxidation number of oxygen in $$\text{O}_2$$ and $$\text{H}_2\text{O}$$.

(c) Based on the changes in oxidation numbers, identify the oxidizing agent and the reducing agent in this reaction.