Period 3 elements & their oxides

0.100 mol of each of the oxides listed is added to separate 1.00 dm³ samples of water.

Which oxide produces the solution with the lowest pH?

Which statement is correct?

Equal amounts of three Period 3 elements are added to separate 100 cm³ samples of water.

Which list is correct when the solutions formed from these elements are arranged in order of decreasing pH?

The oxides P₄O₁₀ and SO₂ both react with water to form acid molecules.

Which row gives the correct shape around the central atom for each acid molecule

This question is about enthalpy changes.

Theoretical values for enthalpies of lattice dissociation can be calculated using a perfect ionic model.

State the meaning of the term perfect ionic model.

Enthalpies of lattice dissociation can also be obtained from Born–Haber cycles.

Figure 3 shows an incomplete Born–Haber cycle for the formation of sodium oxide.

Complete Figure 3 by writing formulas, including state symbols, of the appropriate species on each of the two blank lines.

Table 4 shows some enthalpy changes.

Use the data in Table 4 to calculate the enthalpy of lattice dissociation of sodium oxide.

Explain why the second electron affinity of oxygen has a positive value.

Explain why the enthalpy of lattice dissociation for sodium oxide is greater than the enthalpy of lattice dissociation for sodium chloride.

Sodium chloride dissolves in water.

Table 5 shows some more enthalpy changes.

Use the data in Table 5 to calculate the enthalpy of solution for sodium chloride.

Give a reason why data books do not contain a value for the enthalpy of solution of sodium oxide.

Calculate the temperature, in °C, at which this reaction becomes feasible.

This question is about Period 3 elements and their oxides.

Give an equation for the reaction between phosphorus and an excess of oxygen.

Give an equation for the reaction between sulfur dioxide and water.

Give the displayed formula for the anion formed when sulfur trioxide reacts with water.

Give an equation for the reaction of magnesium with steam.

State one observation made.

Equation

Give an equation to show how an excess of magnesium oxide reacts with

This question is about Period 3 elements and their compounds.

Which is not a correct statement about magnesium hydroxide?

Tick (✓) one box.

Give an equation for the reaction of aluminium oxide with sulfuric acid.

Identify a reagent or test that could be used to distinguish between aqueous solutions of sulfur dioxide and sulfur trioxide with the same concentrations.

State the observation in each case.

Observation with sulfur dioxide solution

Observation with sulfur trioxide solution

The mass spectrum of the element phosphorus has a peak at = 124

Give the formula of the species responsible for this peak.

Give an equation for the reaction of phosphorus(V) oxide with sodium hydroxide solution.

Draw the displayed formula of the molecule formed when phosphorus(V) oxide reacts with water.

Table 4 shows the melting points of three substances.

Explain why the melting points of these substances are different.

You should refer to the structure of and bonding in each substance.

This question is about elements in Period 3 and their compounds.

When a piece of sodium is added to 200 cm³ of water in a large beaker a vigorous reaction occurs. The temperature of the water increases by 25^oC

Give an equation, including state symbols, for the reaction of sodium with water.

Suggest why it is dangerous to react a similar piece of sodium with 10 cm³ of water in a boiling tube.

Equation

Why it is dangerous

Give an equation for the reaction of phosphorus(V) oxide with water.

Suggest a pH for the solution formed.

Equation

Explain, in terms of crystal structure and bonding, why silicon(IV) oxide has a higher melting point than phosphorus(V) oxide.

An element in Period 3 forms an oxide that is insoluble in water. This oxide reacts with sulfuric acid and with aqueous potassium hydroxide.

Give the formula for this oxide.

Give an equation for the reaction of this oxide with sulfuric acid.

Equation

Give the formula of a hydroxide of an element in Period 3 used in medicine.

Identify the element in Period 3, from sodium to chlorine, that has the largest atomic radius.

This question is about Period 3 elements.

Figure 2 shows the second ionisation energies of some elements in Period 3.

Draw a cross (x) on Figure 2 to show the second ionisation energy of silicon.

Identify the element in Period 3, from sodium to argon, that has the highest second ionisation energy.

Give an equation, including state symbols, to show the process that occurs when the second ionisation energy of this element is measured.

If you were unable to identify the element you may use the symbol Q in your equation.

Equation

Explain why the atomic radius decreases across Period 3, from sodium to chlorine.

Identify the element in Period 3, from sodium to chlorine, that has the highest electronegativity.

Phosphorus burns in air to form phosphorus(V) oxide. Give an equation for this reaction.

This question is about oxides.

Sodium oxide forms a solution with a higher pH than magnesium oxide when equal amounts, in moles, of each oxide are added separately to equal volumes of water.

State why both oxides form alkaline solutions.

Suggest why sodium oxide forms a solution with a higher pH than the solution formed from magnesium oxide.

Give an equation for the reaction between phosphorus(V) oxide and water.

In the Contact process, sulfur(IV) oxide is converted into sulfur(VI) oxide using vanadium(V) oxide as a catalyst.

Give two equations to show how the vanadium(V) oxide acts as a catalyst in this process.

This question is about periodicity, the Period 4 elements and their compounds.

State the meaning of the term periodicity.

Identify the element in Period 4 with the highest electronegativity value.

Identify the element in Period 4 with the largest atomic radius. Explain your answer.

The equations for two reactions of arsenic(III) oxide are shown.

Name the property of arsenic(III) oxide that describes its ability to react in these two

Complete the equation for the formation of arsenic hydride.

Sodium thiosulfate reacts with dilute hydrochloric acid as shown.

Give the simplest ionic equation for this reaction.

The gas SO₂ is a pollutant.

State the property of SO₂ that causes pollution when it enters rivers.

Give an equation to show the reaction of SO₂ with water.

Draw a diagram to show the shape of a molecule of H₂O Include any lone pairs of electrons.

State the HOH bond angle.

Explain this shape and bond angle.

Diagram

The initial rate of the reaction between sodium thiosulfate and hydrochloric acid can be monitored by measuring the time taken for a fixed amount of sulfur to be produced.

Describe an experiment to investigate the effect of temperature on the initial rate of this reaction.

Include

• a brief outline of your method

• how you will measure the time taken for a fixed amount of sulfur to be formed

• how you will present your results in graphical form

• a sketch of the graph that you would expect.

This question is about sulfuric acid and its salts.

Draw the displayed formula of a molecule of H₂SO₄

In aqueous solution, sulfuric acid acts as a strong acid. The H₂SO₄ dissociates to form HSO₄ ions and H⁺ ions.

The HSO₄ ions act as a weak acid and dissociate to form SO₄² ions and H⁺ ions.

Give an equation to show each stage in the dissociation of sulfuric acid in aqueous solution.

Include appropriate arrows in your equations.

A student is required to make 250 cm³ of an aqueous solution that contains an accurately measured mass of sodium hydrogensulfate (NaHSO₄).

Describe the method that the student should use to make this solution.

A solution that contains 605 mg of NaHSO₄ in 100 cm³ of solution has a pH of 1.72

Calculate the value of K_a for the hydrogensulfate ion (HSO₄) that is behaving as a weak acid. Give your answer to three significant figures.

Some sodium sulfate is dissolved in a sample of the solution from question 02.4.

Explain why this increases the pH of the solution.

Hydrochloric acid is a strong acid and ethanoic acid is a weak acid.

State the meaning of the term strong acid.

In an experiment, 10.35 cm³ of 0.100 mol dm^–3 hydrochloric acid are added to 25.0 cm³ of 0.150 mol dm^–3 barium hydroxide solution.

Calculate the pH of the solution that forms at 30 °C

Give your answer to 2 decimal places.

The pH of water at 30 °C is 6.92

Give the reason why water is neutral at this temperature.

Identify the oxide that could react with water to form a solution with pH = 2

Tick (✓) one box.

Give the expression for the acid dissociation constant (K_a) for ethanoic acid

A buffer solution contains 0.025 mol of sodium ethanoate dissolved in 500 cm³ of 0.0700 mol dm^–3 ethanoic acid at 25 °C A sample of 5.00 cm³ of 2.00 mol dm^–3 hydrochloric acid is added to this buffer solution.

Calculate the pH of the solution formed.

For ethanoic acid, K_a = 1.76 × 10^–5 mol dm^–3 at 25 °C

This question is about sodium and some of its compounds.

Use your knowledge of structure and bonding to explain why sodium bromide has a melting point that is higher than that of sodium, and higher than that of sodium iodide.

When 250 mg of sodium were added to 500 cm³ of water at 25 °C a gas was produced.

Give an equation for the reaction that occurs. Calculate the volume, in cm³, of the gas formed at 101 kPa

The gas constant, R = 8.31 J K^–1 mol^–1

Calculate the concentration, in mol dm^–3, of sodium ions in the solution produced in the reaction in Question 08.2.

Sodium reacts with ammonia to form the compound NaNH₂ that contains the

Draw the shape of the NH₂^– ion. Include any lone pairs of electrons that influence the shape.

Predict the bond angle. Justify your prediction.

Shape

The elements sodium to sulfur in Period 3 all react with oxygen to form oxides.

Give an equation and two observations made for the reaction that occurs when sodium is heated in oxygen.

Give an equation and one observation made for the reaction that occurs when phosphorus is heated in oxygen.

The melting points of the highest oxides of the elements sodium to sulfur are shown in Table 2.

Explain the increase in melting point from sodium oxide to magnesium oxide.

Explain why the melting point of the oxide of silicon is much higher than that of the highest oxide of phosphorus.

A sample of the highest oxide of phosphorus was prepared in a laboratory.

Describe a method for determining the melting point of the sample. State how the result obtained could be used to evaluate its purity.

Which element forms an ionic oxide that reacts with strong alkalis?