A level Chemistry Transition Metals

Aqueous C₂O₄^2- ions react with MnO₄^- ions in acidic solution according to the equation

5 C₂O₄^2-+ 2MnO- + 16H+ → 2Mn²⁺ + 10CO₂ + 8H₂O

Under the same conditions Fe²⁺ ions also react with MnO₄^- ions. How many moles of MnO₄^- ions are required to react exactly with one mole of Fe(C₂O₄).2H₂O?

• 0.4

• 0.6

• 2.5

• 7.5

Which one of the following electronic configurations is that of a transition element?

• [Ar] 4s²3d¹⁰

• [Ar] 4s²3d⁹

• [Ar] 4s²3d⁰

• [Ar] 4s²3d¹⁰4p¹

The oxidation of ethanedioate (oxalate) ions by manganate(VII) ions can be represented by the half equations:

C₂O₄^2-(aq) → 2CO₂(g) + 2e⁻

MnO₄^- (aq) + 8H+(aq) + 5e− → Mn²⁺(aq) + 4H₂O(l)

What volume (in cm³) of 0.02 M KMnO₄ is required to oxidise completely a solution containing 0.02 mol of ethanedioate ions?

• 25

• 40

• 250

• 400

When vanadium reacts with chlorine at 400°C, a brown compound is obtained. When an aqueous solution containing 0.193 g of this compound was treated with aqueous silver nitrate all the chlorine in the compound was precipitated as silver chloride. The mass of silver chloride (AgCl) produced was 0.574 g. Which one of the following could be the formula of the brown compound?

• VCl

• VCl₂

• VCl₃

• VCl₄

In which one of the following reactions does the metal species undergo reduction?

• MnO₂ + 4HCl → MnCl₂ + 2H₂O + Cl₂

• [Cu(H₂O)₆]²⁺+ 4Cl⁻ → [CuCl₄]²⁻ + 6H₂O

• CrO₇^2- + 2OH⁻ → 2CrO₄^2- + H₂O

• TiO₂ + 2C + 2Cl₂ → TiCl₄ + 2CO

Which one of the following statements is true?

• A blue solution containing the ion [CoCl₄]²⁻ turns pink when added to an excess of water.

• A purple solution is formed when chlorine is bubbled into aqueous sodium bromide.

• A yellow precipitate is formed when aqueous silver nitrate is added to aqueous sodium chloride.

• A green solution containing the ion [CuCl₄]²⁻ turns blue when added to an excess of concentrated hydrochloric acid.

Which of the species given below can behave as ligands?NH₂^- NH₃ NH₄⁺

• all three

• only NH₃

• NH₃ and NH₄⁺

• NH₂^- and NH₃

The percentage of iron in a sample of impure iron(II) sulphate crystals can be determined by titrating solutions, made from separate weighed samples acidified with dilute sulphuric acid, against a standard solution of potassium manganate(VII).Which one of the following would lead to the greatest error in the calculation of the percentage of iron(II) in the sample?

• an error of 0.005 g made when weighing out a sample of mass 0.987 g

• an end-point error of 0.1 cm³ in 25.0 cm³

• an error of 5 cm³ when measuring out 25.0 cm³ of dilute sulphuric acid

• using the average of the titration values 25.4, 25.7 and 25.9 when the correct value is 25.5 cm³

The percentage of iron in a sample of impure iron(II) sulphate crystals can be determined by titrating solutions, made from separate weighed samples acidified with dilute sulphuric acid, against a standard solution of potassium manganate(VII).Which one of the following statements explains why dilute hydrochloric acid is unsuitable for use in this titration?

• HCl will oxidise Fe²⁺ to Fe³⁺

• Cl⁻ will reduce Fe³⁺ to Fe²⁺

• Cl⁻ will reduce MnO₄-

• HCl is a strong acid

Which one of the following can act as an oxidising agent but not as a reducing agent?

• CH₃CHO

• Fe²⁺

• I⁻

• MnO₄^-