Oxidation & reduction in terms of electrons

Two redox systems are shown below.

Which species is the strongest reducing agent?

A Mg²⁺(aq)

B Mg(s)

C Pb²⁺(aq)

D Pb(s)

This question is about the reactions of Group 2 metals and their compounds.

A student adds magnesium to dilute hydrochloric acid in one test tube. The student adds calcium to dilute hydrochloric acid in a second test tube.

A redox reaction takes place in each test tube.

Suggest two observations from the student’s experiment that would show that calcium is more reactive than magnesium.

Write half-equations for the reaction of magnesium with hydrochloric acid.

Oxidation half-equation:........

Reduction half-equation:........

A sample of barium oxide is added to distilled water at 25 °C. A colourless solution forms containing barium hydroxide, Ba(OH)₂.

The solution is made up to 250.0 cm³ with distilled water. The pH of this solution is 13.12.

Determine the mass of barium oxide that was used.

Give your answer to 3 significant figures.

10 cm³ of dilute sulfuric acid is added to 10 cm³ of the colourless solution of Ba(OH)₂

Write an ionic equation, including state symbols, for the reaction.

Limestone and huntite are two calcium minerals.

A typical sample of limestone contains 95.0% by mass of calcium carbonate, CaCO₃

Fertiliser Z, Ca₅NH₄(NO₃)₁₁•10H₂O (M_r = 1080.5 g mol^–1) can be made from limestone.

Calculate the mass, in g, of limestone needed to make 1.50 kg of fertiliser Z.

Give your answer to 3 significant figures.

Huntite is a carbonate mineral with the chemical formula Mg₃Ca(CO₃)₄.

Huntite reacts with dilute hydrochloric acid to produce bubbles of a gas and a colourless solution.

Construct the equation for the reaction. Include state symbols.

This question is about reactions of transition metal compounds.

Explain why ethane-1,2-diamine can act as a bidentate ligand.

The iron(III) ion, Fe³⁺, forms a complex ion A with two ethane-1,2-diamine ligands and two chloride ligands.

Complex ion A has cis and trans stereoisomers. One of these stereoisomers exists as optical isomers.

Determine the empirical formula, with charge, of complex ion A and draw the 3-D structures of the three stereoisomers.

Empirical formula with charge........

Structures

Aqueous sodium hydroxide is added to an aqueous solution of iron(II) sulfate. A pale green precipitate forms which turns brown when left to stand in air.

Write an ionic equation for the formation of the pale green precipitate.

* This question is about copper and copper compounds.

Experiment 1 Hydrochloric acid, HCl (aq), is added to an aqueous solution containing [Cu(H₂O)₆]²⁺ complex ions. A yellow-green solution forms containing complex ion B.

Experiment 2 A piece of copper metal is heated with concentrated sulfuric acid. A reaction takes place forming a pale blue solution C and 45 cm³ of a gas D, measured at RTP. The mass of gas D is 0.12 g.

Experiment 3 An excess of copper(II) oxide is heated with dilute nitric acid. The resulting mixture is filtered. The filtrate is a blue solution E. Aqueous potassium iodide, K I (aq), is added to the blue solution E. A white precipitate F and a brown solution G form.

Determine the formulae of B – G. Construct equations for the reactions taking place, include any changes in oxidation number,

and show your working where appropriate.

This question is about redox reactions.

‘Calcium hypochlorite’, Ca(Cl O)₂, is an ionic compound used in ‘bleaching powder’.

The Cl O^– ion in Ca(Cl O)₂ is the active ingredient that kills bacteria.

Calcium hypochlorite is prepared by reacting chlorine gas with calcium hydroxide.

A student analyses the redox reactions shown below. State symbols have been omitted.

The student concludes that different ions containing chromium can act as oxidising or reducing agents.

Using the terms oxidising agent and reducing agent, and ideas about electrode potentials and equilibrium, explain how the student is correct.

Include overall equations.

A student bubbles hydrogen sulfide gas, H₂S(g), through an acidified solution containing manganate(VII) ions, MnO₄^–(aq).

A redox reaction takes place, forming aqueous manganese(II) ions, a yellow precipitate and one other product.

Construct the equation for this reaction. State symbols are not required.

Two redox systems are shown below.

Which species in the two redox systems is the strongest oxidising agent?

A Fe²⁺(aq)

B Fe(s)

C Cu²⁺(aq)

D Cu(s)

Your answer

Storage cells and fuels cells are types of electrochemical cell.

The electrode potentials for five redox systems are shown in Table 19.1.

A student sets up an electrochemical cell based on redox systems 1 and 4 in Table 19.1.

Draw a labelled diagram to show how this cell could be set up in the laboratory.

Construct the equation for the overall cell reaction.

In acid conditions, MnO₄^2–(aq) disproportionates to form MnO₂(s) and MnO₄^–(aq).

Explain, in terms of oxidation numbers, why disproportionation has taken place.

Explain, in terms of electrode potentials and equilibrium shifts why MnO₄^2– disproportionates in acid conditions. Use the information in Table 19.1.

An alkaline hydrogen-oxygen fuel cell is set up.

The overall equation for the cell reaction is shown below. 2H₂(g) + O₂(g) → 2H₂O(l) Redox system 2 in Table 19.1 is the positive electrode of this cell.

Write the half-equation at the negative electrode.

The cell potential is 1.23 V.

Calculate the electrode potential of the negative electrode.

State one important feature of a fuel cell that is different from a conventional storage cell.

Which reaction is a redox reaction?

A NaCl + AgNO₃ AgCl + NaNO₃

Your answer

This question is about reactions of iron compounds.

In the boxes, write the formulae of A and B.

The student thinks that the reaction of iron(II) sulfide with H⁺ / H₂O is a redox reaction.

Explain, with reasons, whether the student is correct.

Write the equation for the reaction of [Fe(H₂O)₆]²⁺(aq) with Cl₂(g).

Construct an equation for the reaction of H₂S(g) with H⁺(aq)/MnO₄⁻(aq).