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A Level Chemistry > Period 3 > Flashcards

Period 3 Flashcards

1
Q

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.

A

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

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2
Q

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

A

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

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3
Q

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

A

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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4
Q

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

A

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

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5
Q

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

A

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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6
Q

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

A
  • 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
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7
Q

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

A

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

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8
Q

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

A
  • 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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9
Q

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

A

SO3 + 2KOH → K2SO4 + H2O

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10
Q

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

A

number of protons increase
attraction between nucleus and electrons is stronger

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11
Q

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

A

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

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12
Q

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

A

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

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13
Q

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

A

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

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14
Q

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.

A

phosphorus
P4O10 + 6H2O → 4H3PO4

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15
Q

Write an equation for the reaction of sodium with water.

A

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

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16
Q

Write an equation for the reaction of sodium oxide with HCl

A

Na2O + 2HCl → 2NaCl + H2O

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17
Q

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.

A

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

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18
Q

State the meaning of the term amphoteric.

A

Reacts with acids and bases

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19
Q

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

A

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

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20
Q

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

A

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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21
Q

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

A

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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22
Q

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

A

SO2 + H2O → H2SO3
between 1-3

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23
Q

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

A

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

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24
Q

Explain why magnesium has a higher melting point than sodium.

A

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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25
Q

properties of silicon dioxide

A

hard
brittle
not malleable
insulator
non conductor

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26
Q

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.

A

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

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27
Q

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

A

P4O10 + 6MgO → 2Mg3(PO4)

28
Q

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

A

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

29
Q

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

A

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

30
Q

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.

A

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

31
Q

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

A

P4O10 + 12NaOH → 4Na3PO4 + 6H2O

32
Q

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

A

ionic lattice
With strong forces of attraction between oppositely charged ions

33
Q

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

A

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

34
Q

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.

A

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

35
Q

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

A

to prevent it from coming into contact with oxygen/ air

36
Q

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

A

the molecular formula is P4O10
as it exists as P4O10

37
Q

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.

A

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

38
Q

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.

A

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

39
Q

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

A

molecular structure
weak van de waals between molecules

40
Q

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

A

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

41
Q

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

A

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

42
Q

Describe what you would observe when sulfur burns in oxygen

A

blue flame
smelly gas

43
Q

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

A

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

44
Q

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

A

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

45
Q

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

A

insoluble in water

46
Q

What is the structure and bonding in sodium

A

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

47
Q

Which period 3 element has the highest melting point

A

Silicon

48
Q

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.

A

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

49
Q

Write an equation for the reaction of aluminium with oxygen.

A

2Al + 3/2 O2 → Al2O3

50
Q

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

A

insoluble

51
Q

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

A

Al2O3 + 2NaOH + 3H2O → 2NaAl(OH)4

52
Q

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.

A

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

53
Q

Write an equation for the reaction between Na2O and H3PO4

A

3Na2O + 2H3PO4 → 2Na3PO4 + 3H2O

54
Q

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

A

A

55
Q

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)

A

D

56
Q

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

A

Sodium

57
Q

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.

A

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

58
Q

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.

A

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

59
Q

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

A

B

60
Q

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.

A

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

61
Q

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)

A

P4 ^+ (only +1 charge)

62
Q

when do you compare IMFs instead of ionic and covalent bonding

A

when comparing two molecules that have weak covalent bonds

63
Q

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

A
64
Q

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

A
65
Q

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

A
  • has to look tetrahedral
  • has to have 5 bonds on phosphorus
66
Q

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

A

A Level Chemistry (13 decks)

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