Shapes of complex ions

This question is about the chemistry of copper.

Deduce the number of unpaired electrons in a Cu²⁺ ion.

Describe how water acts as a ligand in the formation of [Cu(H₂O)₆]²⁺

A solution of sodium carbonate is added to a blue solution containing

State what is observed.

Give an equation for the reaction.

Equation

When a solution containing [Cu(H₂O)₆]²⁺ ions reacts with an excess of concentrated hydrochloric acid, a ligand exchange reaction occurs.

Blue Yellow

The shape and the colour of the [CuCl₄]^2– ion are different from the shape and the

Explain

• the shape of each complex ion and why these shapes are different

• how colour arises in complex ions

• why the [CuCl₄]^2– ion has a yellow colour, different from the blue colour of the

An excess of water, followed by an excess of concentrated aqueous ammonia, is added to a solution containing [CuCl₄]^2– ions.

State what is observed.

Give an equation for the overall change that occurs.

Equation

A solution contains M₂[Cu(C₂O₄)₂(H₂O)₂] where M is a metal.

A student does a titration to determine the identity of M.

• 2.52 g of solid M₂[Cu(C₂O₄)₂(H₂O)₂] are dissolved in dilute sulfuric acid.

• This solution is transferred to a volumetric flask and made up to 250 cm³ with dilute sulfuric acid.

• A 25.0 cm³ portion is pipetted into a conical flask.

• The mixture in the conical flask is heated to 60 °C and then titrated with 0.0200 mol dm^–3 KMnO₄ solution.

• Several titrations are done and the student’s results are shown in Table 3.

In this titration, only the C₂O₄^2– ions react with the MnO₄^– ions. 2 mol of MnO₄^– ions react with 5 mol of C₂O₄^2– ions.

Give an equation for the reaction between C₂O₄^2– ions and MnO₄^– ions in acidic solution.

Calculate the mean titre from the student’s results.

Calculate the M_r of M₂[Cu(C₂O₄)₂(H₂O)₂]

Identify M.

Draw the structure of two stereoisomers of the complex ion in M₂[Cu(C₂O₄)₂(H₂O)₂] and include the charge on each structure.

Structure 1
Structure 2

Which type(s) of stereoisomerism is/are shown by the complex ion

Which statement is correct?

Which reaction produces an octahedral complex ion ?

Which species has a tetrahedral shape?

Which structure is correct for transplatin?

Which statement about chloride ions is correct?

This question is about complexes of the transition metal chromium.

State the meaning of the term transition metal complex.

Cr(PF₃)₆ is a complex of chromium that contains molecules of PF₃

The electron pair repulsion theory can be used to predict the shape of a PF₃ molecule.

Draw the shape of a PF₃ molecule. Include any lone pairs of electrons that influence the shape.

Name the shape.

Shape

Suggest why the oxidation state of chromium is zero in Cr(PF₃)₆

The compound [Cr(NH₃)₄Cl₂]Cl contains ammonia molecules.

Deduce the oxidation state of chromium in [Cr(NH₃)₄Cl₂]Cl

Name the type of bond between N and H in ammonia.

The compound [Cr(NH₃)₄Cl₂]Cl contains a complex ion that shows isomerism.

Draw the two isomers of the complex ion.

State the type of isomerism shown.

Isomer 1
Isomer 2

Type of isomerism

Complete the equation to show the formation of one complex that contains chromium in its +3 oxidation state.

Which statement about the shapes of ions is not correct?

Copper(II) complexes are coloured. The colour is caused by the d electrons of copper moving from their ground state to an excited state.

Explain why aqueous solutions containing [CuCl₄]^2– ions are yellow.

When a d electron moves from the ground state to the excited state in a copper complex, the energy change is 3.98 x 10^–19 J

Calculate the frequency, in s^–1, of the light absorbed.

State three ways in which a transition metal complex can be changed to alter its colour.

Consider the following reaction scheme in which P, Q and R are different complex ions of copper.

Name the shape of the [CuCl₄]^2– ion.

Give an ionic equation for the conversion of [CuCl₄]^2– to complex ion P.

State the colour of the solution containing the complex ion Q.

Give an ionic equation for the conversion of [CuCl₄]^2– to Q.

Equation

Identify complex ion R.

Which pair of reagents reacts to form a tetrahedral complex?

Which statement about chloride ions is not correct?

Which statement is not correct?

Figure 3 shows some reactions of aqueous iron ions.

Give the formula of Precipitate J and state its colour. Give an equation for Reaction 1.

Equation

Give the formula of L and an equation for Reaction 2.

Equation

Suggest a reagent for Reaction 3.

Give the formula of Precipitate M and state its colour.

Transition metal complexes have different shapes and many show isomerism.

Describe the different shapes of complexes and show how they lead to different types of isomerism. Use examples of complexes of cobalt(II) and platinum(II).

You should draw the structures of the examples chosen.

This question is about vanadium compounds and ions.

Use data from Table 4 to identify the species that can be used to reduce VO₂⁺ ions to VO²⁺ in aqueous solution and no further. Explain your answer.

Give the oxidation state of vanadium in [VO(H₂O)₅]²⁺

The [V(H₂O)₄Cl₂]⁺ ion exists as two isomers. One isomer is shown.

Draw the structure of the other isomer and state the type of isomerism.

Type of isomerism

Heating NH₄VO₃ produces vanadium(V) oxide, water and one other product.

Give an equation for the reaction.

Vanadium(V) oxide is the catalyst used in the manufacture of sulfur trioxide.

Give two equations to show how the catalyst is used and regenerated.

Which complex exists as optical isomers?