Period 3 Flashcards by Aydin Qurashi

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.

4Na + O2 → 2Na2O
Yellow/orange flame/light AND
white solid

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

equation : 4P + 5O2 → P4O10
white light or white fumes

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

Mg^2+ has a greater charge compared to Na^+
there is a stronger ionic bond between Mg^2+ and O^2-

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

SiO2 is a giant macromolecular lattice structure
as P4O10 is a simple molecular

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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

heat sample in a bath
heat sample slowly to establish melting point range
lower melting point as broad range of melting points indicates presence of impurities

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Describe a test you could carry out in a test tube to distinguish between sodium oxide and the phosphorus oxide

react both solutions with water (must add water as you cannot measure pH of solids)
measure pH with a pH meter
pH meter shows that sodium hydroxide has a higher pH than phosphorus oxide
Because sodium hydroxide is a base and Phosphorus oxide forms phosphoric acid (H3PO4) when it reacts with water

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State the type of crystal structure shown in silicon dioxide and in sulfur trioxide.

silicon dioxide : giant macromolecular
sulfur trioxide : simple molecule / molecular

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Explain why silicon dioxide has a higher melting point than sulfur trioxide

covalent bonds in SiO2 are stronger than van de waals between molecules
covalent bonds requires more energy to overcome and van de waals takes less energy to overcome

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Write an equation for the reaction of sulfur trioxide with potassium hydroxide solution

SO3 + 2KOH → K2SO4 + H2O

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Explain why the atomic radii of the elements decrease across Period 3 from sodium to chlorine.

number of protons increase
attraction between nucleus and electrons is stronger

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Explain why the melting point of sulfur (S8) is greater than that of phosphorus (P4)

S8 molecules are bigger than P4 molecules
therefore, van de waals forces between molecules are stronger in sulfur

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Explain why sodium oxide forms an alkaline solution when it reacts with water.

Sodium oxide contains O^2- ions and these O^2- ions react with water forming OH^- ions

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Write an ionic equation for the reaction of phosphorus(V) oxide with an excess of sodium hydroxide solution

P4O10 + 12OH- > 4PO4^3- + 6H2O

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Element X forms an oxide that has a low melting point. This oxide dissolves in water to form an acidic solution.
Identify element X.
Write an equation for the reaction between this oxide of X and water.

phosphorus
P4O10 + 6H2O → 4H3PO4

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Write an equation for the reaction of sodium with water.

2Na + H2O -> 2Na+ + 2OH^- + H2

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Write an equation for the reaction of sodium oxide with HCl

Na2O + 2HCl → 2NaCl + H2O

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Element Z forms an amphoteric oxide that has a very high melting point.
Write the formula of this amphoteric oxide.
Write two equations to show the amphoteric nature of the oxide of Z.

Al2O3
Al2O3 + 6HCl → 2Al3+ + 6Cl- + 3H2O
Al2O3 + 2NaOH + 3H2O → 2Na+ + 2[Al(OH)4]–

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State the meaning of the term amphoteric.

Reacts with acids and bases

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Write an equation for the reaction that occurs when magnesium is heated in steam.
Describe what you would observe when this reaction occurs.

Mg + H2O → MgO + H2
white solid and bright white flame produced

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Explain, in terms of structure and bonding, why sodium oxide has a high melting point.

structure is a giant ionic lattice
strong attraction between oppositely charged ions
lots of energy required to seperate attraction between oppositely charged ions

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Why the melting point of sulfur oxide is different from phosphorus(V) oxide

SO2 is a smaller molecule than P4O10
so van de waals forces between molecules in SO2 are weaker and require less energy to seperate molecules

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Write an equation for the reaction of sulfur(IV) oxide with water.
Suggest the pH value of the resulting solution.

SO2 + H2O → H2SO3
between 1-3

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Silicon(IV) oxide is insoluble in water.
Explain, using an equation, why silicon(IV) oxide is classified as an acidic oxide.

It reacts with alkalis / neutralises bases
SiO2 + 2NaOH -> Na2SiO3 + H2O

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Explain why magnesium has a higher melting point than sodium.

Mg^2+ has a higher charge than Na^+ion
it attracts delocalised sea of electrons more strongly as it has stronger metallic bonding

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properties of silicon dioxide

hard brittle not malleable insulator non conductor

Sulfur(IV) oxide reacts with water to form a solution containing ions. Write an equation for this reaction. With reference to your equation, suggest why sulfur dioxide forms a weakly acidic solution. c) Suggest why silicon dioxide is described as an acidic oxide even though it is insoluble in water.

SO2 + H2O -> H2SO3^- + H^+ partially dissociates as reaction is an equilibrium c) SiO2 reacts with bases

Write an equation for the reaction between the acidic oxide, phosphorus(V) oxide, and the basic oxide, magnesium oxide.

P4O10 + 6MgO → 2Mg3(PO4)

Outline a simple experiment to demonstrate that magnesium oxide has ionic bonding.

Melt the oxide to see molten oxide conducts electricity as it acts as an electrolyte

By reference to the structure of, and the bonding in, silicon dioxide, suggest why it is insoluble in water.

It has a macromolecular structure is has really strong covalent bonds water cannot provide enough energy to break these covalent bonds

State how the melting point of phosphorus(V) oxide compares with that of silicon dioxide. Explain your answer in terms of the structure of, and the bonding in, phosphorus(V) oxide.

lower molecular with covalent bonding weak van de waals forces between molecules do not require much energy to break

Phosphorus(V) oxide is classified as an acidic oxide. Write an equation for its reaction with sodium hydroxide.

P4O10 + 12NaOH → 4Na3PO4 + 6H2O

Explain, in terms of structure and bonding, why sodium oxide has a high melting point.

ionic lattice With strong forces of attraction between oppositely charged ions

Explain, in terms of structure and bonding, why SO3 has a higher melting point than SO2.

SO3 is a larger molecule than SO2 has stronger van de waals forces between molecules

Some Period 3 oxides have basic properties. State the type of bonding in these basic oxides. Explain why this type of bonding causes these oxides to have basic properties.

Ionic contains O^2- ions as these O^2- ions accept a proton to form OH^-

White phosphorus (P4) is a hazardous form of the element. It is stored under water. Suggest why white phosphorus is stored under water.

to prevent it from coming into contact with oxygen/ air

Phosphorus(V) oxide is known as phosphorus pentoxide. Suggest why it is usually represented by P4O10 rather than by P2O5

the molecular formula is P4O10 as it exists as P4O10

Write an equation for the reaction between phosphoric(V) acid and magnesium oxide. B) Explain why an excess of magnesium oxide can be used for this neutralisation.

3MgO + 2H3PO4 → Mg3(PO4)2 + 3H2O B) MgO is insoluble / weakly alkaline / excess MgO can be filtered off

Explain why the use of an excess of sodium hydroxide to neutralise a phosphoric(V) acid solution might lead to environmental problems in the lake.

An excess of NaOH would make the lake alkaline/toxic/kill wildlife

In terms of structure and bonding, explain why sulfur dioxide has a low melting point.

molecular structure weak van de waals between molecules

Write equations for the reactions of Na2O and P4O10 with water. In each case give the approximate pH of the resulting solution.

a) Na2O + H2O -> 2Na+ + 2OH– 14 b) P4O10 + 6H2O -> 4H3PO4 0 (between -1 and +2 accepted)

Describe what you would observe when magnesium burns in oxygen. Write an equation for the reaction that occurs.

white flame white fumes 2Mg + O2 -> 2MgO

Describe what you would observe when sulfur burns in oxygen

blue flame smelly gas

Explain why sodium oxide reacts to form an alkaline solution when added to water.

O2- ions react with water accepting a proton forming OH^- ions

Outline an experiment that could be used to show that aluminium oxide contains ions.

heat until molten do not allow in water identify it is an electrode as it conducts electricity

Suggest one reason why a thin layer of aluminium oxide protects aluminium from corrosion in moist air.

insoluble in water

What is the structure and bonding in sodium

Giant metallic lattice Strong electrostatic attraction between metal ions and delocalised electrons.

Which period 3 element has the highest melting point

Silicon

Predict whether the melting point of lithium oxide is higher than, the same as, or lower than the melting point of sodium oxide and explain your prediction.

Higher Li+ smaller than Na+ Attracts O2- more strongly

Write an equation for the reaction of aluminium with oxygen.

2Al + 3/2 O2 → Al2O3

Suggest one property of the aluminium oxide coating that causes aluminium to resist corrosion in water.

insoluble

Write an equation for the reaction between aluminium oxide and an excess of aqueous sodium hydroxide.

Al2O3 + 2NaOH + 3H2O → 2NaAl(OH)4

Silicon dioxide does not react with hydrochloric acid but it does react with sodium hydroxide. State one property of silicon dioxide that can be deduced from this information and write an equation for its reaction with sodium hydroxide.

SiO2 is acidic SiO2 + 2NaOH -> Na2SiO3 + H2O

Write an equation for the reaction between Na2O and H3PO4

3Na2O + 2H3PO4 → 2Na3PO4 + 3H2O

Which element forms an ionic oxide that reacts with strong alkalis? A Aluminium B Magnesium C Sodium D Sulfur

Which is the formula of the main aluminium-containing species present when aluminium oxide is added to an excess of water? A [Al(H2O)6]3+(aq) B Al(H2O)3(OH)3(s) C [Al(H2O)2(OH)4]−(aq) D Al2O3(s)

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

Sodium

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.

Oxide ions react with water to form hydroxide ions sodium hydroxide more soluble than magnesium hydroxide

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.

V2O5 + SO2 → V2O4 + SO3 V2O4 + 1/2 O2 → V2O5

This question is about Period 3 elements and their compounds. (a) Which is not a correct statement about magnesium hydroxide? a) It is used to neutralise stomach acid b) It forms a solution with pH = 14 at 25 °C c) It has the empirical formula H2MgO2

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.

reagent : pH meter observation with sulfur dioxide : 2-3 pH observation with sulfur trioxide : 1-2 pH or reagent : universal indicator observations : orange - red red

The mass spectrum of the element phosphorus has a peak at = 124 Give the formula of the species responsible for this peak. (mass number of phosphorus = 31)

P4 ^+ (only +1 charge)

when do you compare IMFs instead of ionic and covalent bonding

when comparing two molecules that have weak covalent bonds

Draw displayed formula of undissociated acid formed when sulfur dioxide reacts with water

Draw displayed formula of molecule formed when phosphorus oxide reacts with water

- has to look tetrahedral - has to have 5 bonds on phosphorus

Give displayed formula of molecule formed when phosphorus oxide reacts with water

Period 3 Flashcards

(69 cards)