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Sams Chemistry > Period 3 - Trend Spotting > Flashcards

Period 3 - Trend Spotting Flashcards

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1
Q

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

3 marks

A

M1.(a) Mg + H2O → MgO + H2
ignore state symbols

M2.(b)
White solid / powder / ash / smoke
ignore precipitate ignore fumes
(Bright) white light / flame
allow glow
penalise effervescence under list principle
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2
Q

Write an equation for the reaction that occurs when sodium is heated in oxygen. Describe what you would observe when this reaction occurs.
Equation …………………………………………………………………………………………… Observations

3 marks

A 
2Na +   O2 → Na2O / 4Na + O2 → 2Na2O
Allow multiples, ignore state symbols Allow 2Na + O2 → Na2O2
white / yellow    solid / ash / smoke
ignore precipitate ignore fumes
orange / yellow flame
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3
Q

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

2 marks

A

Ionic lattice / giant ionic

Strong ATTRACTION between OPPOSITELY CHARGED IONS / Na+ and O2−
OR
lots of energy required to separate / overcome attraction between oppositely charged ions / Na+ and O2−

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4
Q

Use data from the table above to predict a value for the melting point of sulfur(IV) oxide.

Suggest, in terms of structure and bonding, why the melting point of sulfur(IV) oxide is different from that of phosphorus(V) oxide.

3 marks

A

200 (K)
Allow range 10−273 (K)

SO2 smaller (molecule) (than P4O10) (or converse)
also SO2 has lower Mr / less surface area / less polarisable / fewer electrons

vdW forces between molecules are weaker / require less energy to separate molecules

ignore dipole−dipole

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5
Q

Write an equation for the reaction of sulfur(IV) oxide with water.

Suggest the pH value of the resulting solution.
Equation ……………………………………………………

2 marks

A

SO +H2O→2H+ +SO2−

Allow between values of 1-3

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6
Q

Silicon(IV) oxide is insoluble in water.

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

A

Reacts with / neutralises bases / alkalis

Allow any given base or alkali including OH−
SiO2 + 2NaOH ࢐Na2SiO3 + H2O
Allow CaO + SiO2 → CaSiO3 or equation with any suitable
base

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7
Q

Magnesium oxide, silicon dioxide and phosphorus(V) oxide are white solids but each oxide has a different type of structure and bonding.

State the type of bonding in magnesium oxide.
Outline a simple experiment to demonstrate that magnesium oxide has this type of bonding.

Type of bonding

Experiment …….

A

MgO is ionic
Do not allow incorrect formulae for ions.

Melt it
(Molten oxide) conducts electricity
Allow acts as an electrolyte.

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8
Q

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

A

The number of protons increases (across the period) / nuclear charge increases

Therefore, the attraction between the nucleus and electrons increases

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9
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 der Waals / dispersion / London forces between molecules are stronger in sulfur

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10
Q

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

A

Sodium oxide contains O2– ions
These O2– ions react with water forming OH– ions
O2– + H2O —> 2OH– scores M1 and M2

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11
Q

This question is about some Period 3 elements and their oxides.

Describe what you would observe when, in the absence of air, magnesium is heated strongly with water vapour at temperatures above 373 K.
Write an equation for the reaction that occurs.
Observations ………………………………………….
Equation ……….

A

White powder / solid / ash / smoke Ignore ppt / fumes
Bright / white light / flame

Allow glows white / glows bright
Mg + H2O → MgO + H2

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12
Q

Explain why magnesium has a higher melting point than sodium

A

Mg2+ / magnesium ion has higher charge than Na+
AllowMg2+ ionssmaller/greaterchargedensitythanNa+ ions
Allow Mg atoms smaller than Na (atoms)
Allow magnesium has more delocalised electrons Must be a comparison
Ignore reference to nuclear charge

Attracts delocalised / free / sea of electrons more strongly / metal–metal bonding stronger / metallic bonding stronger

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13
Q

State the structure of, and bonding in, silicon dioxide.
Other than a high melting point, give two physical properties of silicon dioxide that are characteristic of its structure and bonding.
Structure
Bonding
Physical property 1
Physical property 2

A 
Structure: Macromolecular / giant molecule / giant covalent Mark independently
Bonding: Covalent / giant covalent
Physical Properties:
Any two from: Hard/
Brittle / not malleable
Insoluble
Non conductor
Ignore correct chemical properties Ignore strong, high boiling point, rigid
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14
Q

Sulfur(IV) oxide reacts with water to form a solution containing ions.
Write an equation for this reaction. ……….

A

SO2 +H2O→H+ +HSO-

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15
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)2

OR P4O10 + 6MgO → 6Mg2+ + 4PO43-

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16
Q

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

A

Na2O is an ionic lattice / giant ionic / ionic crystal
CE= 0 if molecules, atoms, metallic mentioned Mention of electronegativity max 1 out of 2

With strong forces of attraction between ions
Allow strong ionic bonds / lots of energy to separate ions

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17
Q

Explain, in terms of structure and bonding, why sulfur trioxide has a higher melting point than sulfur dioxide.

A

SO3 is a larger molecule than SO2
Allow greater Mr / surface area
So van der Waals’ forces between molecules are stronger

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18
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.
Type of bonding …………………………………………………….. Explanation .

A

Ionic
Do not allow ionic with covalent character

ContainsO2− ions/oxideions
Equations of the form O2− + H+ → OH− / O2− + 2H+ → H2O / O2−
+ HO → 2OH− score M2 and M3 2

These/O2− ions(acceptprotonsto)formOH− /hydroxide/water(mustscore M2 to gain M3)

19
Q

Sulfur dioxide reacts with water to form a weakly acidic solution.

(i) Ions are formed when sulfur dioxide reacts with water. Write an equation for this reaction.
………

A

SO2 +H2O→H+ +HSO− 3
Allow2H+ +SO32− butnoions,nomark

Reversible reaction

20
Q

Suggest why silicon dioxide is described as an acidic oxide even though it is insoluble in water.
……………………..

A

SiO2 reacts with bases / NaOH / CaO / CaCO3

21
Q

In terms of structure and bonding, explain why sodium oxide has a high melting point

A

Ionic lattice / solid / giant ionic

Strong (electrostatic) forces/attraction between ions

22
Q

sulfur dioxide has a low melting point.

A

Molecular/molecules

Weak dipole-dipole and/or van der Waals forces between molecules

23
Q

Explain why the melting point of P4O10 is higher than the melting point of SO2

A

P4O10 bigger molecule/has larger surface area than SO2

van der Waals forces between molecules stronger

24
Q

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

A

Na2O + H2O 2Na+ + 2OH–
Allow 2NaOH

14
Allow 12–14

P4O10 + 6H2O 4H3PO4
Allow ions

0
Allow –1 to +2

25
Q

Write an equation for the acid–base reaction that occurs when Na2O reacts with P4O10 in the absence of water.

A

6Na2O + P4O10 —> 4Na3PO4

Allow ionic

26
Q

Sodium, aluminium and silicon are solid elements with a silver colour. These elements react with oxygen to form oxides with high melting points. Aluminium is a reactive metal, but it resists corrosion in water because it has a surface coating of aluminium oxide.

In terms of its structure and bonding, explain why silicon dioxide has a high melting point…………

A

Macromolecular
Or giant molecule
Or giant covalent (also gains M2) Do not allow giant atomic
Ionic/metallic CE=0 for all 3 marks

Covalent bonding (between atoms)
Do NOT allow if between molecules
Lose both bonding marks if contradiction e.g. mention of intermolecular forces

Many/strong bonds to be broken (or lots of energy required)

27
Q

State the type of bonding in aluminium oxide. ……………………….

A

Al2O3 ionic

28
Q

Write an equation for the reaction of aluminium with oxygen

A

2Al+3/2O2 →Al2O3

29
Q

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

A

Insoluble/impermeable/non-porous

Or does not react/inert

30
Q

Sodium metal is not resistant to corrosion in water, despite having a surface coating of sodium oxide. Write an equation to show how sodium oxide reacts with water

A

Na2O + H2O → 2NaOH

31
Q

Aluminium oxide is amphoteric. It reacts with acids and alkalis.

Write an equation for the reaction between aluminium oxide and hydrochloric acid.
……….

A

Al2O3 +6HCl→2AlCl3 +3H2O

32
Q

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

A

Al2O3 +2NaOH+3H2O→2NaAl(OH)4

Other equations with Al2O3 are possible e.g. AlO +2OH– +3HO→2[Al(OH)]–

33
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.
Property …..
Equation ….

A

SiO2 acidic/Lewisacid/electron pair acceptor

SiO2 +2NaOH→Na2SiO3 +H2O

34
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 coming into contact/reacting with oxygen/air

35
Q

Phosphorus(V) oxide is known as phosphorus pentoxide.

Suggest why it is usually represented by P4O10 rather than by P2O5

A

One molecule contains 4P and 10O/the molecular formula is P4O10

36
Q

Explain why phosphorus(V) oxide has a higher melting point than sulfur(VI) oxide.

A

P4O10 is a bigger molecule (than SO3)/greater Mr/more electrons/ greater surface area

37
Q

Write an equation for the reaction of P4O10 with water to form phosphoric(V) acid. Give the approximate pH of the final solution.
Equation ………………………………………………………………………………………….. pH …………………………………………………..

A

P4O10 + 6H2O —>4H3PO4
Allow correct ionic equations Ignore state symbols
pH must be in the range –1 to +2

38
Q

Explain why an excess of magnesium oxide can be used for this neutralisation.

A

MgO is sparingly soluble/insoluble/weakly alkaline

39
Q

A waste-water tank was contaminated by P4O10. The resulting phosphoric(V) acid solution was neutralised using an excess of magnesium oxide. The mixture produced was then disposed of in a lake

Write an equation for the reaction between phosphoric(V) acid and magnesium oxide.

A

3MgO + 2H3PO4 → Mg3(PO4)2 +3H2O
OR
MgO+2H3PO4 →Mg(H2PO4)2 +H2O

40
Q

Explain why the use of an excess of sodium hydroxide to neutralise the 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

41
Q

Describe what you would observe when magnesium burns in oxygen. Write an equation for the reaction that occurs. State the type of bonding in the oxide formed.
Observations

Equation

Type of bonding

A

white flame / white light
Mark flame independent of other observations

solid / powder / smoke / ash / white fumes
penalise precipitate
penalise wrong colour
if more than one observation for M2 apply list principle. (If an observation is incorrect, the incorrect observation negates a correct one

2Mg+O2 →2MgO
ignore state symbols allow multiples

ionic

42
Q

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

A

(heat until) molten
or dissolve in molten cryolite
do not allow solution in water

conducts electricity / can be electrolysed

43
Q

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

A

insoluble (in water)

44
Q

Write an ionic equation in each case to show how aluminium oxide reacts with the following

(i) hydrochloric acid ……………………………………………………………………………………………….
(ii) aqueous sodium hydroxide

A

Al2O3 +6H+ 2Al3+ +3H2O

ii) AlO +2OH– +3HO→2Al(OH)–
or
AlO +6OH– +3HO→2Al(OH)3–

Sams Chemistry (16 decks)

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