DP Chemistry Questionbank

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):

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

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.

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 why experiments involving tetracarbonylnickel are very hazardous.

Suggest how the change of iodine concentration could be followed.

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

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

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

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)

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

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

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

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

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.

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

Which of the following does not react with dilute HCl(aq)?

A.     Na₂CO₃

B.     Cu

C.     Zn

D.     CuO

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)

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

State the oxidation half-equation.

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

Determine the oxidation state of nitrogen in the two reactants.

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

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.

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

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 ${\mathrm{MnCl}}_2$.

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

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 ${\mathrm{MnCl}}_2$.

Suggest a metal that could replace nickel in a new half-cell and reverse the electron flow. 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⁺.

Identify the best reducing agent in the table above.

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)

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

What is correct for this redox reaction?

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

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.

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.

Which coefficients correctly balance this redox equation?

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

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

The three steps of the Winkler Method are redox reactions.

Deduce the reduction half-equation for step II.

The three steps of the Winkler Method are redox reactions.

Deduce the reduction half-equation for step II.

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

Deduce the half-equation for this reduction reaction.

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

Deduce the equation for this redox reaction.

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

Deduce the half-equation for this reduction reaction.

Which is correct for the reaction?

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

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

Deduce the equation for this redox reaction.

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

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

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

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

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

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.

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

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.

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

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

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

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

Deduce the average oxidation state of carbon in product B.

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

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.

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.

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

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

Deduce the average oxidation state of carbon in product B.

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.

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.

State the name of this compound, applying IUPAC rules.

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

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

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

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