Properties of ionic compounds

Tutton’s salts are ‘double salts’ with the formula X₂Y(ZO₄)₂ • 6H₂O.

A Tutton’s salt contains two cations: X⁺ and Y²⁺.

• X + can be an ion of the Group 1 elements K, Rb, Cs or Fr, or an ammonium ion.

• Y²⁺ can be a 2+ ion of magnesium or an ion of most of the transition elements in Period 4.

• Z can be S or Cr.

(NH₄)₂Cu(SO₄)₂ • 6H₂O is an example of a Tutton’s salt.

Predict the formula of a Tutton’s salt containing different ions from (NH₄)₂Cu(SO₄)₂ • 6H₂O.

A student prepares a sample of the Tutton’s salt, (NH₄)₂Cu(SO₄)₂ • 6H₂O using the method shown below.

Step 1 Dissolve 0.025 mol of ammonium sulfate and 0.025 mol of hydrated copper(II) sulfate, CuSO₄ • 5H₂O, in water and make up to 50 cm³.

Step 2 Boil the resulting mixture for 2 minutes and allow to cool.

Step 3 Allow the solvent to evaporate slowly. Pale blue crystals of the Tutton’s salt form.

What masses are needed of ammonium sulfate and CuSO₄ • 5H₂O?

mass of ammonium sulfate........ g

mass of CuSO₄ • 5H₂O........ g

In Step 3, why does the student allow the solvent to evaporate and not boil off all the solvent in Step 2 ?

The student dissolves their Tutton’s salt in water. A pale blue solution forms.

The student carries out two tests on this aqueous solution.

The student adds an excess of aqueous ammonia to their aqueous solution of Tutton’s salt. A deep blue solution forms.

The complex ion responsible for the deep blue solution has a molar mass of 167.5 g mol^–1.

Suggest the formula of this complex ion.

The student adds NaOH(aq) to the aqueous solution of Tutton’s salt and warms the mixture.

A precipitate and a gas are formed.

Write the formulae of the precipitate and gas and suggest a test that could confirm the identity of the gas.

Formula of precipitate........

Formula of gas........

Test to confirm the identity of the gas........

How could the student carry out a test-tube test to confirm the anion in the Tutton’s salt?

These questions are from different areas of chemistry.

Ammonia, NH₃, and ammonium nitrate, NH₄NO₃, are compounds of nitrogen.

The boiling point of NH₃ is –33 °C.

The boiling point of NH₄NO₃ is 210 °C.

Explain why there is a large difference in boiling points.

Two students discuss the oxidation numbers in ammonium nitrate, NH₄NO₃.

One student claims that the two nitrogen atoms have the same oxidation number. The other student disagrees and claims that the nitrogen atoms have different oxidation numbers.

Explain with reasons which student is correct.

What are the percentage compositions of copper and zinc in the brass sample?

Calculate the relative atomic mass of zinc in the sample of brass.

Give your answer to 2 decimal places.

Fill in the table to predict the splitting patterns in the proton NMR spectrum of the

The table shows the chemical shifts for the peaks in the proton NMR spectrum at proton environments 2 and 3.

Proton environment	2	3
Chemical shift,	2.5 ppm	3.6 ppm

Suggest why the peaks for proton environments 2 and 3 have the chemical shifts which are shown in the table.

Glycine, H₂NCH₂COOH, is an -amino acid.

Glycine reacts with NaOH to form the salt H₂NCH₂COONa.

Glycine reacts with HCl to form the salt HOOCCH₂NH₃Cl.

The salts have different H–N–H bond angles.

State the different H–N–H bond angles and explain why they are different.

H₂NCH₂COONa H–N–H bond angle =........ °

HOOCCH₂NH₃Cl H–N–H bond angle =........ °

Glycine reacts with aqueous copper(II) ethanoate to form copper(II) glycinate, Cu(H₂NCH₂COO)₂, and ethanoic acid. Copper(II) glycinate is a complex which exists as two square planar isomers.

Write an equation for this reaction and draw the structures of the two square planar isomers of the complex Cu(H₂NCH₂COO)₂.

equation

This question is about organic acids.

Table 18.1 shows the R groups in four amino acids.

Most amino acids show optical isomerism.

Explain the term optical isomerism.

Draw 3-D diagrams to show the optical isomers of alanine.

How many optical isomers does threonine have?

Ibuprofen, shown below, is used as a painkiller.

What is the molecular formula of ibuprofen?

One ibuprofen tablet contains 400 mg of ibuprofen.

Calculate the number of ibuprofen molecules in one ibuprofen tablet.

Give your answer to 3 significant figures.

Tablets based on ibuprofen and lysine are now available from pharmacies.

These tablets are claimed to act faster than ibuprofen by being absorbed into the body more quickly than ibuprofen alone.

One type of these tablets contains a salt of ibuprofen and the amino acid lysine (R = –(CH₂)₄NH₂) in a 1:1 molar proportion.

Suggest why tablets based on a salt of ibuprofen should act faster in the body than ibuprofen.

In the Periodic Table, element X is in Group 2 and element Y is in Group 15 (5).

What is the likely formula of an ionic compound of X and Y ?

A X₂Y₅

B X₂Y₃

C X₃Y₂

D X₅Y₂

Your answer

Which statement about ammonium carbonate is not correct?

A It reacts with Ba(NO₃)₂(aq) to form a white precipitate.

B It effervesces with dilute nitric acid.

C It release an alkaline gas with warm NaOH(aq).

D It has the formula NH₄CO₃.

Your answer

Select an element from the first three periods that fits each of the following descriptions.

The element that forms a 1– ion with the same electron configuration as helium.

The element with the highest first ionisation energy.

The element in Period 3 which has the successive ionisation energies shown below.

The element which forms a compound with fluorine that has octahedral molecules.

An element which reacts with water to form an acidic solution.

The element X, which forms a compound with hydrogen, XH₃, with a molar mass of 34.0 g mol^–1.

An element which forms a compound with hydrogen in which the element has an oxidation number of –4.

The element which has a density of 1.33 × 10^–3 g cm^–3 at room temperature and pressure.

Table 1.1 shows some properties of Period 3 chlorides.

Explain the properties shown in Table 1.1 in terms of bonding and structure.