Which coefficients correctly balance this redox equation?

aFe²⁺(aq) + MnO₄⁻(aq) + bH⁺(aq) → cFe³⁺(aq) + Mn²⁺(aq) + dH₂O(l)

Determine the oxidation state of vanadium in each of the following species.

Bromate(V) ions act as oxidizing agents in acidic conditions to form bromide ions.

Deduce the half-equation for this reduction reaction.

Deduce the overall redox equation for the reaction between acidic Sn²⁺(aq) and Cr₂O₇^2–(aq), using section 24 of the data booklet.

Identify the best reducing agent in the table above.

Deduce, giving reasons, whether the reaction of magnesium nitride with water is an acid–base reaction, a redox reaction, neither or both.

Deduce, giving reasons, whether the reaction of magnesium nitride with water is an acid–base reaction, a redox reaction, neither or both.

Suggest how the change of iodine concentration could be followed.

Suggest a metal that could replace nickel in a new half-cell and reverse the electron flow. Use section 25 of the data booklet.

Which of the following is a redox reaction?

A. 3Mg (s) + 2AlCl₃ (aq) → 2Al (s) + 3MgCl₂ (aq)

B. SiO₂ (s) + 2NaOH (aq) → Na₂SiO₃ (aq) + H₂O (l)

C. KCl (aq) + AgNO₃ (aq) → AgCl (s) + KNO₃ (aq)

D. 2NaHCO₃ (aq) → Na₂CO₃ (aq) + CO₂ (g) + H₂O (l)

Which equation shows oxygen undergoing reduction?

A.     2F₂ + O₂ → 2F₂O

B.     Na₂O + H₂O → 2NaOH

C.     H₂O₂ + 2HI → 2H₂O + I₂

D.     2CrO₄²⁻ + 2H⁺ $\rightleftharpoons$ Cr₂O₇²⁻ + H₂O

Which of the following is not a redox reaction?

A.     CH₄(g) + Cl₂(g) → CH₃Cl(g) + HCl(g)

B.     C(s) + O₂(g) → CO₂(g)

C.     2CO(g) → CO₂(g) + C(s)

D.     CH₃COOH(aq) + NaOH(aq) →  CH₃COONa(aq) + H₂O(l)

State the oxidation half-equation.

Molten zinc chloride undergoes electrolysis in an electrolytic cell at 450 °C.

Deduce the half-equations for the reaction at each electrode.

Calculate the oxidation state of sulfur in iron(II) disulfide, FeS₂.

Suggest why experiments involving tetracarbonylnickel are very hazardous.

Determine the oxidation state of nitrogen in the two reactants.

Which is correct for the reaction?

P₄ (s) + 3H₂O (l) + 3OH⁻ (aq) → PH₃ (g) + 3H₂PO₂⁻ (aq)

Bromate(V) ions act as oxidizing agents in acidic conditions to form bromide ions.

Deduce the half-equation for this reduction reaction.

State the name of this compound, applying IUPAC rules.

Bromate(V) ions oxidize iron(II) ions, Fe²⁺, to iron(III) ions, Fe³⁺.

Deduce the equation for this redox reaction.

State the oxidation number of carbon in sodium carbonate, Na₂CO₃.

State the oxidation number of carbon in sodium carbonate, Na₂CO₃.

Deduce the average oxidation state of carbon in product B.

Which is the species oxidized and the oxidizing agent in the reaction?

MnO₂ (s) + 4HCl (aq) → MnCl₂ (aq) + Cl₂ (g) + 2H₂O (l)

What are the oxidation states of chromium in (NH₄)₂Cr₂O₇ (s) and Cr₂O₃ (s)?

MnO₂ is another possible catalyst for the reaction. State the IUPAC name for MnO₂.

The three steps of the Winkler Method are redox reactions.

Deduce the reduction half-equation for step II.

What is the name of the compound with formula Ti₃(PO₄)₂?

A. Titanium phosphate

B. Titanium(II) phosphate

C. Titanium(III) phosphate

D. Titanium(IV) phosphate

Which experimental methods could be used to observe the progress of the following reaction?

Cr₂O₇^2-(aq) + 6I^-(aq) + 14H⁺(aq) → 2Cr³⁺(aq) + 3I₂(aq) + 7H₂O(l) 

I. Change in colour 
II. Change in mass 
III. Change in electrical conductivity 

A.  I and II only 

B.  I and III only 

C.  II and III only 

D.  I, II and III

Identify, from the table, a non-vanadium species that can reduce VO²⁺(aq) to V³⁺(aq) but no further.

State the name of this compound, applying IUPAC rules.

Describe how the relative reactivity of rhenium, compared to silver, zinc, and copper, can be established using pieces of rhenium and solutions of these metal sulfates.

Which element is reduced in the following decomposition?

(NH₄)₂Cr₂O₇(s) → N₂(g) + Cr₂O₃(s) + 4H₂O(g)

A.     N

B.     H

C.     Cr

D.     O

Discuss why different methods of reduction are needed to extract metals.

Deduce the redox equation for the reaction of nickel(II) chloride solution with the metal identified in (b)(i).

MnO₂ is another possible catalyst for the reaction. State the IUPAC name for MnO₂.

Describe how the relative reactivity of rhenium, compared to silver, zinc, and copper, can be established using pieces of rhenium and solutions of these metal sulfates.

What is the order of decreasing reactivity of the metals (most reactive first)?

Zn(s) + Sn²⁺(aq) → Zn²⁺(aq) + Sn(s)
Cu(s) + Zn²⁺(aq) → No Reaction
Sn(s) + Cu²⁺(aq) → Sn²⁺(aq) + Cu(s)
Ag(s) + Cu²⁺(aq) → No Reaction

A.     Zn > Cu > Sn > Ag

B.     Sn > Zn > Ag > Cu

C.     Ag > Cu > Zn > Sn

D.     Zn > Sn > Cu > Ag

Nickel is also used as a catalyst. It is processed from an ore until nickel(II) chloride solution is obtained. Identify one metal, using sections 24 and 25 of the data booklet, which will not react with water and can be used to extract nickel from the solution.

Formulate an equation for the reaction between VO²⁺(aq) and V²⁺(aq) in acidic solution to form V³⁺(aq).

A reaction takes place when a rechargeable battery is used:

Pb(s) + PbO₂(s) + 4H⁺(aq) + 2SO₄²⁻(aq) → 2PbSO₄(s) + 2H₂O(l)

Which statements are correct?

I.     H⁺ is reduced
II.     The oxidation state of Pb metal changes from 0 to +2
III.     PbO₂ is the oxidising agent

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

Identify, from the table, a non-vanadium species that could convert ${\text{VO}}_2^{+}\text{(aq)}$ to V²⁺(aq).

What is the oxidation half-equation in the redox reaction?

2S₂O₃^2–(aq) + I₂(aq) → S₄O₆^2–(aq) + 2I^–(aq)

A.     I₂(aq) + 2e^– → 2I^–(aq)

B.     2I^–(aq) → I₂(aq) + 2e^–

C.     2S₂O₃^2–(aq) → S₄O₆^2–(aq) + 2e^–

D.     S₄O₆^2–(aq) + 2e^– → 2S₂O₃^2–(aq)

Which element is reduced in the following decomposition?

(NH₄)₂Cr₂O₇(s) → N₂(g) + Cr₂O₃(s) + 4H₂O(g)

A.     N

B.     H

C.     Cr

D.     O

Formulate an equation for the oxidation of nickel(II) sulfide to nickel(II) oxide.

What is the change in the oxidation state of oxygen?

2Fe²⁺(aq) + H₂O₂(aq) + 2H⁺(aq) → 2H₂O (l) + 2Fe³⁺(aq)

A.  +1

B.  0

C.  −1

D.  −2

Magnesium chloride can be electrolysed.

(i) Deduce the half-equations for the reactions at each electrode when molten magnesium chloride is electrolysed, showing the state symbols of the products. The melting points of magnesium and magnesium chloride are 922K and 987K respectively.

(ii) Identify the type of reaction occurring at the cathode (negative electrode).

(iii) State the products when a very dilute aqueous solution of magnesium chloride is electrolysed.

Deduce, giving a reason, which species is the reducing agent.

Bromate(V) ions oxidize iron(II) ions, Fe²⁺, to iron(III) ions, Fe³⁺.

Deduce the equation for this redox reaction.

Deduce the average oxidation state of carbon in product B.

How many electrons are needed when the following half-equation is balanced using the lowest possible whole numbers?

__ NO₃^– (aq) + __ H⁺(aq) + __ e^– → __ NO (g) + __ H₂O (l)

A.  1

B.  2

C.  3

D.  5

The combustion reaction in (f)(ii) can also be classed as redox. Identify the atom that is oxidized and the atom that is reduced.

Deduce the coefficients required to complete the half-equation.

ReO₄⁻ (aq) + ____H⁺ (aq) + ____e⁻ ⇌ [Re(OH)₂]²⁺ (aq) + ____H₂O (l)        E^θ = +0.36 V

Magnesium chloride can be electrolysed.

Deduce the half-equations for the reactions at each electrode when molten magnesium chloride is electrolysed, showing the state symbols of the products. The melting points of magnesium and magnesium chloride are 922 K and 987 K respectively.

Anode (positive electrode):

Cathode (negative electrode):

Deduce, referring to oxidation states, whether ${\mathrm{MnO}}_2$ is an oxidizing or reducing agent.

In acidic solution, bromate ions, BrO₃⁻(aq), oxidize iodide ions, I⁻(aq).

BrO₃⁻(aq) + 6H⁺(aq) + 6e⁻ $\rightleftharpoons$ Br⁻(aq) + 3H₂O(l)

2I⁻(aq) $\rightleftharpoons$ I₂(s) + 2e⁻

Formulate the equation for the redox reaction.

What is correct for this redox reaction?

MnO₂(s) + 2$\text{I}$⁻ (aq) + 4H⁺(aq) → Mn²⁺(aq) + $\text{I}$₂(aq) + 2H₂O (l)

The three steps of the Winkler Method are redox reactions.

Deduce the reduction half-equation for step II.

Which is a correct statement for the reaction below? 

2MnO₄^-(aq) + 6H⁺(aq) + 5NO₂^-(aq) → 2Mn²⁺(aq) + 5NO₃^-(aq) + 3H₂O(l) 

A. MnO₄^- is the reducing agent and the oxidation number of Mn increases.
B. MnO₄^- is the oxidizing agent and the oxidation number of Mn decreases. 
C. NO₂^- is the reducing agent and the oxidation number of N decreases. 
D. NO₂^- is the oxidizing agent and the oxidation number of N increases.

Suggest a metal that could replace nickel in a new half-cell and reverse the electron flow. Use section 25 of the data booklet.

The following occurs when metal X is added to Y sulfate solution and Z sulfate solution. (X, Y and Z represent metal elements but not their symbols.)

X (s) + YSO₄ (aq) → XSO₄ (aq) + Y (s)
X (s) + ZSO₄ (aq): no reaction

What is the order of increasing reactivity?

A.  X < Y < Z

B.  Y < X < Z

C.  Z < Y < X

D.  Z < X < Y

The nickel obtained from another ore, nickeliferous limonite, is contaminated with iron. Both nickel and iron react with carbon monoxide gas to form gaseous complexes, tetracarbonylnickel, $\text{Ni(CO}{\text{)}}_{\text{4}}\text{(g)}$, and pentacarbonyliron, $\text{Fe(CO}{\text{)}}_{\text{5}}\text{(g)}$. Suggest why the nickel can be separated from the iron successfully using carbon monoxide.

Write the half-equation for the reduction of hydrogen peroxide to water in acidic solution.

Deduce a balanced equation for the oxidation of Fe2+ by acidified hydrogen peroxide.

Formulate an equation for the reaction between VO²⁺(aq) and V²⁺(aq) in acidic solution to form V³⁺(aq).

Deduce, referring to oxidation states, whether ${\mathrm{MnO}}_2$ is an oxidizing or reducing agent.

State the oxidation state of manganese in ${\mathrm{MnO}}_2$ and ${\mathrm{MnCl}}_2$.

State the oxidation state of manganese in ${\mathrm{MnO}}_2$ and ${\mathrm{MnCl}}_2$.

Compare the ease of oxidation of s-block and d-block metals to their melting points and densities. Use section 25 of the data booklet.

Consider the following half-equations:

I₂ (s) + 2e^– $\rightleftharpoons$ 2I^– (aq)                 E^θ = +0.54 V
(brown)          (colourless)

MnO₄^– (aq) + 8H⁺ (aq) + 5e^– $\rightleftharpoons$ Mn²⁺ (aq) + 4H₂O (l)                 E^θ = +1.51 V
(purple)                                      (colourless)                                                         

Which statement is correct for the reaction between KMnO₄ (aq) and KI (aq) in acidic conditions?

A. MnO₄^– reduces I^– to I₂.

B. I^– reduces MnO₄^– to Mn²⁺.

C. The colour changes from brown to purple.

D. MnO₄^– is oxidized to Mn²⁺.

Deduce the half-equations for the reaction at each electrode.

Deduce the overall cell reaction including state symbols. Use section 7 of the data booklet.

Suggest an experiment that shows that magnesium is more reactive than zinc, giving the observation that would confirm this.

Compare the ease of oxidation of s-block and d-block metals to their melting points and densities. Use section 25 of the data booklet.

Suggest an experiment that shows that magnesium is more reactive than zinc, giving the observation that would confirm this.

Which combination best describes what is happening to chloromethane, CH₃Cl, in the equation below?

CH₃Cl (g) + H₂(g) $\rightleftharpoons$ CH₄(g) + HCl (g)

A.  Oxidation and addition

B.  Oxidation and substitution

C.  Reduction and addition

D.  Reduction and substitution

Deduce the overall cell reaction including state symbols. Use section 7 of the data booklet.