Oxidation and Reduction in Term of Change of Oxidation Number

Find the oxidation number of sulphur in Na₂S₂O3.

What is the oxidation number of sulphur in K₂SO₃?

What is the oxidation number of vanadium in V₂O₅?

What is the oxidation state of nitrogen in a nitric acid molecule?

What is the oxidation state of phosphorus in a phosphoric acid molecule?

What is the oxidation number of hydrogen in magnesium hydride, \(\mathrm{MgH}_2\) ?

Which of the underlined element in the following compounds has the highest oxidation number?

Which of the following is true about the oxidation number of the elements in NH₄ClO₃.

What is the oxidation number of \(\mathrm{X}\) in \(\mathrm{XO}_4^{-}\)?

What is the oxidation number of the chromium element in potassium dichromate(VI), \(\mathrm{K}_2 \mathrm{Cr}_2 \mathrm{O}_7\) ?

The following ionic equation represents the reaction between acidified potassium dichromate(VI) solution and iron(II) sulphate solution.
\[
\mathrm{Cr}_2 \mathrm{O}_7^{2-}+14 \mathrm{H}^{+}+6 \mathrm{Fe}^{2+} \rightarrow 6 \mathrm{Fe}^{3+}+2 \mathrm{Cr}^{3+}+7 \mathrm{H}_2 \mathrm{O}
\]
What is the change of oxidation number of chromium in the reaction?

The following equation represents the oxidation reaction between ethanol and acidified potassium dichromate(VI).
\[
\begin{aligned}
& 3 \mathrm{C}_2 \mathrm{H}_5 \mathrm{OH}+2 \mathrm{~K}_2 \mathrm{Cr}_2 \mathrm{O}_7+8 \mathrm{H}_2 \mathrm{SO}_4 \rightarrow \\
& \quad 3 \mathrm{CH}_3 \mathrm{COOH}+2 \mathrm{Cr}_2\left(\mathrm{SO}_4\right)_3+2 \mathrm{~K}_2 \mathrm{SO}_4+11 \mathrm{H}_2 \mathrm{O}
\end{aligned}
\]

What is the change in the oxidation number of the element chromium in this reaction?

Diagram 6 shows the chemical formula of a compound.

                       
the IUPAC name and oxidation number of copper element in the compound?

\begin{align}
\begin{array}{|c|l|c|}
\hline & \text { Name of compound } & \begin{array}{l}
\text { Oxidation number of } \\
\text { copper element }
\end{array} \\
\hline \text { A } & \text { Copper(I) oxide } & +1 \\
\hline \text { B } & \text { Copper(I) oxide } & +2 \\
\hline \text { C } & \text { Copper(II) oxide } & +1 \\
\hline \text { D } & \text { Copper(II) oxide } & +2 \\
\hline
\end{array}
\end{align}

The following chemical equation represents the extraction of silicon from quartz using coke.
\[
\mathrm{SiO}_2+\mathrm{C} \longrightarrow \mathrm{Si}+\mathrm{CO}_2
\]
What is the change in oxidation number of silicon?

The following ionic equation shows the reaction between zinc and acid.
\[
\mathrm{Zn}(\mathrm{s})+2 \mathrm{H}^{+}(\mathrm{aq}) \rightarrow \mathrm{Zn}^{2+}(\mathrm{aq})+\mathrm{H}_2(\mathrm{~g})
\]
What is the change in oxidation number of hydrogen?

Which of the following IUPAC names are correct for the respective formulae of substances?

The equation below shows the decomposition of potassium chlorate.

2KClO₃ → 2KCl + 3O₂

Which of the following shows the change of oxidation number of chlorine in the reaction?

The equation represents the redox reaction between ammonia and copper(II) oxide.

2NH₃ + 3CuO → N₂ + 3Cu + 3H₂O

Which of the following is true about the reaction?

The oxidation number of calcium increases when

Which of the underlined substances in the following equations undergo oxidation?

Which of the following statements about a chemical reaction are true?

A substance undergoes oxidation if

Which of the following indicates that a substance undergoes reduction?

Which of the following is NOT true about oxidation and reduction?

Which of the underlined substances in the following equations undergo oxidation?

The half equation represents the reduction reaction of acidified potassium dichromate(VI) solution.
\[
\mathrm{Cr}_2 \mathrm{O}_7^{2-}+\mathrm{xH}^{+}+\mathrm{ye}^{-} \longrightarrow \mathrm{zCr}^{3+}+7 \mathrm{H}_2 \mathrm{O}
\]
What are the value of \(x, y\) and \(z\) ? 

\begin{align}
\begin{array}{|c|c|c|c|}
\hline & x & y & z \\
\hline \text { A } & 14 & 6 & 2 \\
\hline \text { B } & 14 & 5 & 1 \\
\hline \text { C } & 7 & 2 & 1 \\
\hline \text { D } & 7 & 1 & 2 \\
\hline
\end{array}
\end{align}