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A Level chemistry past paper questions > Topic 1 > Flashcards

Topic 1 Flashcards

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1
Q

Which of the following ionisations requires a greater amount of energy than that for the process Mg(g) –> Mg+(g)?

a) Al(g) –> Al+(g)
b) Ba(g) –> Ba+(g)
c) Mg+(g) –> Mg2+(g)
d) Na(g) –> Na+(g)

A

C

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2
Q

Ions which under the same conditions, would be deflected in a mass spectrometer by the same amount as 12C2+ include

a) 12C+
b) 6Li+
c) 14N2+
d) 13C2+

A

b

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3
Q

The measured relative atomic mass of oxygen is 16.5 in a particular sample.
Which one of the following statements is not correct?

a) each atom of oxygen contains eight protons
b) the relative molecular mass of the sample is 33.0
c) there are at least two isotopes of oxygen in this sample
d) the mass spectrum of this sample shows a peak for the O+ ion at m/z = 16.5

A

d

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4
Q

In a mass spectrometer the isotopes of an element are separated and two measurements are made for each isotope

Which two measurements are made for each isotope?

A

m/z

relative abundance

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5
Q

Why is a mass spectrometer incapable of distinguishing between the ions 14N+ and 14N2 2+?

A

same m/z

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6
Q

Explain why the values shown on the graph go down from magnesium to
aluminum, and then rise again going from aluminum to silicon.

A

Mg –> Al
Electron removed from Al is from a higher energy level (3p rather than 3s)

Al –> Si
Si has one more proton than Al and has greater nuclear charge. The electrons removed in both cases are 3p

Electron removed from Si is closer to nucleus (than Al)

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7
Q

Complete the sketch graph for the elements from phosphorus to argon.
Explain why one of these elements does not follow the general trend

A

S does not follow trend
S has one (3)p orbital which has two paired electrons and is fully occupied
A paired electron is easier to remove

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8
Q

Sodium and magnesium are both in Period 3. In sodium iodide, the ions are not
polarized but in magnesium iodide some polarization occurs.

Explain the term polarization as it applies to magnesium iodide, and state
how it arises.

A

I- anion becomes distorted and is not spherical
Therefore Mg2+ has higher charge and a smaller radius
Bonding in magnesium iodide has some covalent character

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9
Q

State how thermochemical data could be used to show that there is polarization in magnesium iodide

A

Born Haber cycle and theoretical calculated lattice energies are different

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10
Q

In the context of the Periodic Table, explain what is meant by the term
periodicity

A

A repeating trend across a period /across each period

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11
Q

Name one of the elements that is composed of simple molecules at
room temperature and pressure

A

Phosphorus or Sulfur or Chlorine

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12
Q

Explain why the melting temperature of magnesium is higher than that of
sodium

A

Mg2+ ions are smaller than Na+ ions
magnesium has more delocalised electrons (than sodium)
more (heat) energy is needed to break the metallic bonds in Mg than in Na

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13
Q

What are the 2nd and 3rd stages of mass spectrometry

A

acceleration

deflection

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14
Q

Explain why a potassium ion is smaller than a potassium atom

A

Electrons in the ion are held more tightly

So there is less repulsion between remaining electrons

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15
Q

Which type of metals have the lowest ionisation energies

A

alkaline metals

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16
Q

Nuclear power stations are often proposed as suitable alternatives to those
burning coal, gas or oil.
Suggest a country where, because of its location, the dangers of nuclear power may outweigh the advantages. Justify your answer

A

Italy with volcanoes

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17
Q

Suggest the formulae of the hydrides of arsenic and selenium

A

AsH3 / H3As

H2Se / SeH2

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18
Q

Explain why the first ionization energy of selenium is lower than that of
arsenic

A

In Se, (spin) pairing has occurred (for the first time in that p sub-shell)
There is then an increase in repulsion so electrons are lost more easily

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19
Q

Explain why the first ionization energy of krypton is higher than that of selenium

A

The nuclear charge is increasing

electron is removed from the same sub shell

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20
Q

Explain why the first ionization energy of rubidium is lower than that of krypton

A

Rb outer electron is in another shell further from nucleus

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21
Q

Which of the elements, arsenic to rubidium, is likely to have atoms with the
smallest atomic radius?

A

Kr

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22
Q

Explain why the first ionization energy of the elements down Group 1 decreases even though the atomic number increases

A

Atomic radius increases and there is more shielding

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23
Q

Explain why the successive ionization energies in sodium increase

A

effective nuclear charge increases

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24
Q

Explain why, in moving from Na to Ar, the general trend is for the first ionization
energy to increase

A

atomic number increases
Shielding of the nucleus is about the same
Distance from nucleus is less

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25
Q

Estimate the value of the first ionization energy of potassium,

A

200 – 490

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26
Q

What is the structure and bonding in
Na
Si
S

A

giant and metallic
giant and covalent
simple and covalent

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27
Q

Explain why silicon has a much higher melting temperature than sulfur.

A

Si : covalent bonds

S : weak force e.g London forces

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28
Q

Explain why the melting temperature increases from sodium to aluminium

A

Cations/ions decrease in size, so attraction between cations and delocalised electrons increases

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29
Q

Magnesium forms the basic oxide magnesium oxide, MgO. This oxide is almost
insoluble in water. On gentle warming with dilute sulfuric acid, magnesium oxide reacts to form aqueous magnesium sulfate solution.

Describe how you would use the above reaction to prepare a pure sample of
magnesium sulfate.

A 
Add MgO to acid
Filter
Heat/boil filtrate
leave to crystallise
Leave to dry
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30
Q

Suggest what action should be taken if a pupil spilt a small quantity of dilute
sulfuric acid on a laboratory bench

A

Rinse with plenty of water

31
Q

Strontium sulfate is produced when aqueous sodium sulfate is added to aqueous strontium chloride.
Give the ionic equation for the reaction, including state symbols

A

Sr2+(aq) + SO4 2−(aq)→ SrSO4(s)

32
Q

State what would be seen when concentrated sulphuric acid is added to separate solid samples of each of these compounds.

a) Lithium Chloride
b) Sodium Bromide
c) Potassium Iodide

A

a) white fumes
b) brown vapour
c) purple vapour

33
Q

Write an equation for the reaction between concentrated sulfuric acid and solid lithium chloride
Include state symbols

A

LiCl2(s) + H2SO4(l) –> HCl(s) + LiHSO4(g)

34
Q

When sodium chlorate(1), NaClO, is heated, sodium chlorate (V) and sodium chloride are formed

a) write an ionic equation for this
b) what type of reaction is this

A

a) 3OCl- –> ClO3- + 2Cl-

b) disproportionate

35
Q

2IO3 +5SO2 + 4H20 –> I2 +8H+ (5SO4)2-

Has SO2 been oxidised or reduced?

A

Oxidised because Sulfur has lost electrons

36
Q

Name a reagent that could be used to identify if a solution contains Iodine and what state would be seen

A

Starch

Blue/ black

37
Q

How would you confirm that a solution supposedly being HCl contained chloride ions

A

Add dilute silver nitrate acid
White precipitate formed
Soluble in dilute ammonia

38
Q

Hydrogen chloride is soluble in water. Explain why the solution is acidic.

A

Dissociates forming H+ ions which makes the solution acidic

39
Q

Give a chemical test for chlorine stating what you’ll see and what you’d do

A

Bleach damp litmus paper

40
Q

Sodium Iodide react with concentrated sulphuric acid to give iodine, not hydrogen iodide.

Explain why iodides react differently compared to chlorides in this situation

A

Iodide is more easily oxidised than HCl because it’s larger than Chlorine

41
Q

2H2SO4 + 2NaBr –> Br2 + SO2 +2H2O + Na2SO4

a) Write the oxidation numbers at the start and end of the reaction for sulfur and bromine
b) Explain why the numbers in the balanced equation are consistent with the changes in oxidation number

A

Sulfur initially 6+ goes to +4
Bromine initally -1 goes to 0

b) An increase in Br oxidation number = 2 x 1/2
One S decreases in oxidation number by 2

42
Q

HCl- 188 boiling point
HBr- 206 boiling point
HI- 238 boiling point

Explain the trend in the boiling points of the hydrogen halides

A

Going down the group, the number of electrons increases

So Van der Waals forces between molecules increases

43
Q

Predict a value for the bp of HF and explain your reason for this

A

200-300 K

Hydrogen bonding is present which is a stronger intermolecular force between molecules

44
Q

Define reduction in terms of changing oxidation numbers

A

Decrease in oxidation number

45
Q

Balance the equation of sodium bromide with concentrated sulfuric acid

2NaBr + H2SO4 –> NaHSO4 + SO2 + Br2 + H2O

A

2NaBr + 3H2SO4 –> 2NaHSO4 + SO2 + Br2 + 2H2O

46
Q

2NaBr + 3H2SO4 –> 2NaHSO4 + SO2 + Br2 + 2H2O

Use the changes in oxidation number of sulfur to show that the halides become more powerful reducing agents as the groups are descended

A

Change in oxidation number of S increases down the halides group

S 6+ –> 4+

47
Q

Complete an equation for the hydrolysis of bromine with water which is a disproportionation reaction

A

Br2(aq) + H2O(I) 2H+(aq) + Br-(aq) + BrO-(aq)

48
Q

Explain using oxidation numbers, why the reaction: Br2(aq) + H2O(I) 2H+(aq) + Br-(aq) + BrO-(aq) is known as disproportionation

A

Bromine has been both oxidised and reduced

From 0 to +1 and -1

49
Q

Write the ionic equation for the reaction of chlorine gas with bromide ions

A

Cl2(g) + 2Br-(aq) –> 2Cl-(aq) + Br2(aq)

50
Q

Balance the equation

Br2 + H2O + SO2 –> H+ + Br- + (SO4)2-

A

Br2 + 2H2O + SO2 –> 4H+ + 2Br- + (SO4)2-

51
Q

State a fault that may occur in a procedure and recording of measurements when doing a titration

A

Only doing 1 titration

Not reading to 0.05cm3

52
Q

State and explain the type of reaction that occurs when chlorine attacks a metal, using the example of iron

A

Redox reaction as chlorine removes/gains electrons from the metal and the metal gives/loses electrons to the chlorine

53
Q

Suggest a reason why the use of chlorine is undesirable in swimming pools

A

Chlorine is highly toxic

54
Q

Give the formula for calcium chlorate (1)

A

Ca(ClO)2

55
Q

Discuss and explain the science community’s advice that CFC’s should no longer be used in aerosols, foams and refrigerants. Support your answer with one or more equations

A

CFC are greenhouse gases
because their dipole moment changes when they vibrate
and so contribute to global warming
depletion of the ozone later which causes less ozone to absorb UV radiation which causes skin cancer

Cl. + O3 –> ClO. + O2
ClO. + O. –> Cl. + O2

56
Q

Bottle C labelled magnesium carbonate contains a white powder. When heated this powder produces a colourless gas that turns limewater cloudy.
State whether this label is correct and explain your answer

A

Limewater turns milky therefore CO2

MgCO3 decomposes on heating to CO2 therefore the label is correct

57
Q

Describe a test to show that the solid in bottle D is barium hydroxide and not magnesium hydroxide

A

Substance on wire in flame, goes pale green for barium, while there would be no colour for magnesium

58
Q

Bottle E is clearly labelled magnesium nitrate. When a sample of the chemical is heated it gives off a brown gas and a gas that relights a glowing splint
Give the name of each of the gases formed and write an equation for this chemical reaction

A

Oxygen given off
NO2 given off –> brown gas

2Mg(NO3)2 –> 2MgO + 4NO2 +O2

59
Q

Explain the origin of the flame colour

A

Electrons excited so fall to a lower energy level and give out energy in the form of light

60
Q

What is meant by the term polarising power as applied to cations

A

The ability of cations to distort the electron cloud around an anion

61
Q

Why is it easier to decompose magnesium nitrate than barium nitrate by heating

A

Magnesium ion is smaller than the barium ion and so has a higher change density so the polarising power increases this weakens the bonds in the nitrate

62
Q

State and explain the trend in thermal stability of the carbonates of the Group 2 elements as the group is descended

A

Thermal stability increases as cation size increases so therefore polarises the carbonate ion

63
Q

Magnesium oxide is a basic oxide which produces an alkaline solution with water. Write an equation to show how the oxide ion, O2-, acts as a base in the reaction with water

A

O2- +H2O –> 2OH-

64
Q

Write the equations to show the action of heat on the following solid nitrates.

a) LiNO3
b) CsNO3

A

a) 4LiNO3 –> 2Li2O + 4NO2+O2

b) 2CsNO3 –> 2CsNO2 + O2

65
Q

What difference would you expect to see after calcium metal and barium metal have reacted with water

A

Calcium would go cloudy but barium goes clear

66
Q

The reaction between barium metal and excess dilute sulphuric acid stops after a very short time. Suggest an explanation for this

A

Insoluble coating of barium sulphate formed which prevents acid getting to the surface of barium

67
Q

Write the ionic equation for the reaction of calcium metal with dilute hydrochloric acid

A

Ca(s) + 2H+(aq) –> Ca2+(aq) + H2(g)

68
Q

When a small piece of barium is added to water, the barium gets smaller and eventually disappears

State TWO other observations you could make

A

Gets warm

Fizzing

69
Q

Which concentrated acid should be used to dissolve a carbonate of a group 2 metal to carry out a flame test

a) ethanoic acid
b) hydrochloric acid
c) nitric acid
d) sulfuric acid

A

hydrochloric acid

70
Q

What colour does a barium salt give in a flame test

a) colourless
b) green
c) red
d) yellow-red

A

b

71
Q

Separate flame tests are carried out with lithium, sodium, potassium, magnesium, calcium and strontium salts. How many of these metal ions would colour the flame red?

A

C

72
Q

A group 2 element reacts vigorously with water to produce a soluble hydroxide which forms a white precipitate when neutralised by sulfuric acid and forms a carbonate which is very stable to heat.
The element could be

a) magnesium
b) calcium
c) strontium
d) barium

A

d

73
Q

The group 2 metals, considered in order of increasing atomic number show a decrease in

a) first ionisation energy
b) nuclear charge
c) chemical reactivity
d) ionic radius

A

a

A Level chemistry past paper questions (5 decks)

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