Redox

The equation below represents a redox reaction involving iron(II) chloride and chlorine gas. $2\text{FeCl}_2 + \text{Cl}_2 \rightarrow 2\text{FeCl}_3$ Which equation represents the reduction step in this reaction?

May/June 2015

This equation represents a redox reaction between iron(II) chloride and chlorine gas. $2\text{FeCl}_2 + \text{Cl}_2 \rightarrow 2\text{FeCl}_3$ Which equation represents the reduction process in this reaction?

May/June 2015

Titanium can be produced by heating titanium(IV) chloride, $\text{TiCl}_4$, together with magnesium.

May/June 2015

Which equation is not a redox reaction?

May/June 2016

Gaseous compound X acts as an oxidising agent. X is passed as bubbles through separate solutions of aqueous potassium iodide and acidified potassium manganate(VII). Which row shows the colour changes observed when X is bubbled through these two solutions?

May/June 2016

Which statement is not a description of a reduction reaction?

May/June 2016

Copper is made to react with hot concentrated aqueous sulfuric acid. $\text{Cu}(s) + 2\text{H}_2\text{SO}_4(aq) \rightarrow \text{CuSO}_4(aq) + \text{SO}_2(g) + 2\text{H}_2\text{O}(l)$

May/June 2017

Which reactions include oxidation and reduction?

May/June 2018

Copper(II) oxide reacts with carbon on heating. $2\text{CuO} + \text{C} \rightarrow 2\text{Cu} + \text{CO}_2$ Which of the following statements about this reaction is correct?

May/June 2018

Gas X changes acidified potassium manganate(VII) from purple to colourless. Gas Y changes aqueous potassium iodide from colourless to brown. What do these observations indicate about gas X and gas Y?

May/June 2019

Reduction may be described using the gain or loss of oxygen, hydrogen or electrons. Which row gives the correct description of all three definitions of reduction?

May/June 2019

In which of these equations is the change shown for the underlined species correct? 1. (oxidation) $\underline{\text{CH}_4} + 2\text{O}_2 \rightarrow \underline{\text{CO}_2} + 2\text{H}_2\text{O}$ 2. (reduction) $2\text{H}_2\underline{\text{S}} + \text{SO}_2 \rightarrow \underline{3\text{S}} + 2\text{H}_2\text{O}$ 3. (reduction) $\text{BrO}_3^- + 5\underline{\text{Br}^-} + 6\text{H}^+ \rightarrow \underline{3\text{Br}_2} + 3\text{H}_2\text{O}$

May/June 2021

X is a colourless solution. A few drops of aqueous potassium iodide solution are introduced into a sample of X. There is no visible change. Y is also a colourless solution. A few drops of aqueous acidified potassium manganate(VII) solution are added to a sample of Y. The purple colour of the potassium manganate(VII) vanishes. What can be inferred about X and Y from these two observations?

May/June 2021

Concentrated hydrochloric acid is oxidised by manganese(IV) oxide, $\text{MnO}_2$. Which two substances are produced in this reaction?

May/June 2022

The table shows details about four redox reactions. Which row correctly states what is oxidised and the evidence that this is oxidation?

May/June 2022

What observation is made during an oxidation process?

May/June 2022

An excess of aqueous iodide ions is added to acidified aqueous potassium manganate(VII). Which row is correct?

May/June 2022

Methane combustion is a redox reaction. $\text{CH}_4 + 2\text{O}_2 \rightarrow \text{CO}_2 + 2\text{H}_2\text{O}$ Which of the following statements about this reaction is correct?

May/June 2023

Which preparation method for magnesium sulfate is an example of a redox reaction?

May/June 2023

If a piece of copper is added to aqueous silver nitrate, a displacement reaction occurs. What is the ionic equation for the reaction that occurs?

May/June 2023

Iron(II) ions undergo reaction with chlorine. $2\text{Fe}^{2+}(aq) + \text{Cl}_2(g) \rightarrow 2\text{Fe}^{3+}(aq) + 2\text{Cl}^-(aq)$ Which statement is correct for this reaction?

May/June 2023

Which reagent and which observation are used for the test for a reducing agent?

May/June 2023

A lot of reactions involve oxidation and reduction. Which statement is correct?

May/June 2024

Pick one item from the list below to respond to the questions. anhydrous copper(II) sulfate calcium carbonate carbon monoxide chlorine ethanoic acid iron methanoic acid methanol nickel silicon(IV) oxide vanadium(V) oxide A substance may be selected once, selected several times, or not selected at all.

May/June 2024

Magnesium combines with oxygen to produce magnesium oxide. $2\text{Mg} + \text{O}_2 \rightarrow 2\text{MgO}$ Which row is the correct one?

May/June 2025

In which reaction does nitric acid behave as an oxidising agent?

Oct/Nov 2015

In which reaction does nitric acid behave as an oxidising agent?

Oct/Nov 2015

Which of the reactions is not a redox reaction?

Oct/Nov 2016

Chlorine reacts with iron(II) ions. $2\text{Fe}^{2+}(aq) + \text{Cl}_2(g) \rightarrow 2\text{Fe}^{3+}(aq) + 2\text{Cl}^-(aq)$ Which of the following statements about this reaction is correct?

Oct/Nov 2016

Which reaction does not involve a redox reaction?

Oct/Nov 2016

During paper production, sulfur dioxide is added to take away the yellow colour from the wood pulp. Which term can be used to describe sulfur dioxide in this process?

Oct/Nov 2016

Which change takes place every time a metal atom is oxidised?

Oct/Nov 2017

Numerous reactions involve oxidation and reduction. Which statement is correct?

Oct/Nov 2018

Which reaction is a redox reaction?

Oct/Nov 2018

In which reaction is the underlined substance undergoing reduction?

Oct/Nov 2019

In which reaction does the underlined substance undergo reduction?

Oct/Nov 2019

Which statements regarding oxidation and reduction are correct?

Oct/Nov 2021

Aqueous ammonium nitrite, $\text{NH}_4\text{NO}_2$, breaks down on heating. $\text{NH}_4\text{NO}_2(\text{aq}) \rightarrow \text{N}_2(\text{g}) + 2\text{H}_2\text{O}(\ell)$ For this salt, the anion is ......1...... . During the reaction, the nitrogen atoms in the ......2...... ion are oxidised. Which formulae correctly fill gaps 1 and 2?

Oct/Nov 2021

The equation represents the reaction between glucose and oxygen. $\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O}$. Which statement regarding this reaction is correct?

Oct/Nov 2021

Magnesium is oxidised when it reacts with aqueous silver nitrate. $\text{Mg} + 2\text{Ag}^+ \rightarrow \text{Mg}^{2+} + 2\text{Ag}$

Oct/Nov 2021

In which reaction is the substance that is underlined reduced?

Oct/Nov 2022

Which change causes a decrease?

Oct/Nov 2022

Thiosulfate ions, $\text{S}_2\text{O}_3^{2-}$, undergo reaction with iodine, $\text{I}_2$, in aqueous solution. $2\text{S}_2\text{O}_3^{2-}(aq) + \text{I}_2(aq) \rightarrow 2\text{I}^-(aq) + \text{S}_4\text{O}_6^{2-}(aq)$ During this reaction, the $\text{S}_2\text{O}_3^{2-}$ ions ........1........ electrons and are ........2........ . Which words best fill gaps 1 and 2?

Oct/Nov 2022

Which change results in a reduction?

Oct/Nov 2022

When the conditions are right, iron reacts with chlorine to produce iron(III) chloride. $2\text{Fe} + 3\text{Cl}_2 \rightarrow 2\text{FeCl}_3$ Which of the following statements about this reaction is correct?

Oct/Nov 2022

In which substance is the oxidation number of the nitrogen atom the same as that of the nitrogen atom in $\text{HNO}_2$? For the other elements in these compounds, take the following oxidation numbers: $\text{H}, +1;\ \text{F}, -1;\ \text{O}, -2.$

Oct/Nov 2023

Chlorine, $\text{Cl}_2$, undergoes reaction with iron(II), $\text{Fe}^{2+}$, ions. $\text{Cl}_2 + 2\text{Fe}^{2+} \rightarrow 2\text{Cl}^- + 2\text{Fe}^{3+}$ Which of the following statements about this reaction is correct?

Oct/Nov 2023

Copper produces a red oxide, $\text{Cu}_2\text{O}$, and a black oxide, $\text{CuO}$. When a catalyst is present, aqueous hydrogen peroxide, $\text{H}_2\text{O}_2$, decomposes to make water. The black oxide contains copper in a .....1..... oxidation state than the red oxide does. When water is formed, hydrogen peroxide is .....2...... . Which words correctly fill gaps 1 and 2?

Oct/Nov 2024

Peroxodisulfate ions, $\text{S}_2\text{O}_8^{2-}$, undergo reaction with iron(II) ions, $\text{Fe}^{2+}$. $\text{S}_2\text{O}_8^{2-} + 2\text{Fe}^{2+} \rightarrow 2\text{SO}_4^{2-} + 2\text{Fe}^{3+}$. In this reaction, sulfur and iron are the only elements that are oxidised or reduced. Which row is correct?

Oct/Nov 2024