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A level Chemistry Past Papers > AS Chemistry Inorganic and Physical 2020 > Flashcards

AS Chemistry Inorganic and Physical 2020 Flashcards

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1
Q

There is a general trend for an increase in ionisation energy across Period 3.
Give one example of an element that deviates from this trend and explain why (3 marks)

A
  • Aluminium
  • Outer electron in 3p orbital
  • 3p orbital is of slightly higher energy than 3s/ slightly more shielded
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2
Q

The student uses a funnel to fill the burette for titration. After filling, the student forgets to remove the funnel from the top of the burette.
Suggest why this might affect the titre volume recorded. (1 mark)

A
  • Additional drops of solution could have entered the burette from the funnel, (making the value on the burette lower)
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3
Q

Advantage if a conical flask rather than beaker for titration (1 mark)

A
  • Less chance of losing any solution using a conical flask when swirling
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4
Q

Define relative atomic mass (2 marks)

A
  • The average mass of an atom of an element

- compared to 1/12th of the mass of an atom of carbon-12

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5
Q

Define enthalpy change of a chemical reaction (1 mark)

A
  • Heat energy change at constant pressure
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6
Q

The student uses the data to determine a value for the enthalpy change.
Explain how the experimental method and use of apparatus can be improved to provide more accurate data.
Describe how this data from the improved method can be used to determine an accurate value for the temperature change. (6 marks)

A

Stage 1: Apparatus
1a. Use a burette/pipette (instead of a measuring cylinder)
1b. Use a polystyrene cup (instead of a beaker) / insulate beaker
1c. Reweigh the watchglass after adding the solid
1d: Use powdered solid
Stage 2: Temperature Measurements
2a. Measure and record the initial temperature of the solution for a few minutes before addition
2b. Measure and record the temperature after the addition at regular intervals (eg each minute) for 8+ minutes/until a trend is observed
Stage 3: Temperature Determination
3a. Plot a graph of temperature against time
3b. Extrapolate to the point of addition
3c. Determine ΔT at the point of addition

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7
Q

Suggest how the percentage uncertainty in the temperature change can be reduced in the titration without changing the apparatus (1 mark)

A
  • Increase the concentration of the solutions
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8
Q

Explain why the melting point of magnesium is higher than the melting point of sodium (2 marks)

A
  • Mg2+ has a higher charge than Na+ / Mg has
    more delocalised electrons than Na
  • Stronger attraction to delocalised sea of electrons / stronger metallic
    bonding
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9
Q

Give an equation to show how magnesium is used as the reducing agent in the
extraction of titanium.
Explain, in terms of oxidation states, why magnesium is the reducing agent. (2 marks)

A
  • 2Mg + TiCl4 → 2MgCl2 + Ti

- Mg changes oxidation state from 0 to +2 so electrons are lost

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10
Q

State what is observed when dilute aqueous sodium hydroxide is added to separate
solutions of magnesium chloride and barium chloride. (2 marks)

A
  • With MgCl2: (slight) white precipitate

- With BaCl2: no (visible) change/reaction

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11
Q

Shape of NCl3 (1 mark)

A
  • Pyramidal
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12
Q

Shape of NCl4+ (1 mark)

A
  • Tetrahedral
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13
Q

Bond angle of NCl4+ and explanation of it (2 marks)

A
  • 109.5º

- 4 bp and electron pairs repel equally to be as far apart as possible

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14
Q

Give one reason why water is treated with chlorine. (1 mark)

A
  • kill bacteria
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15
Q

Explain why chlorine is added to water even though it is toxic (1 mark)

A
  • health benefit outweighs risk / only used in small

quantities

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16
Q

Give an equation for the reaction of chlorine with cold water (1 mark)

A

Cl2 + H2O ⇌ HCl + HClO

17
Q

A student completes an experiment to determine the percentage by mass of
sodium chloride in a mixture of sodium chloride and sodium iodide. Silver nitrate is added to the solution.
Suggest why an excess is used (1 mark)

A
  • To ensure that all the halide ions (chloride and iodide) are removed from the solution
18
Q

A student does an experiment to determine the relative molecular mass (Mr) of liquid A using a gas syringe in an oven and a needle. The student noticed that some of the liquid injected into the gas syringe
did not vaporise.
Explain the effect that this has on the Mr calculated by the student. (2 marks)

A
  • Calculated Mr value would be greater than actual

- A lower volume would have been recorded

19
Q 
Which species contains bonds that have different polarities?
A NH4+
B CCl4
C CH3Cl
D H3O+
A

C

CH3Cl

20
Q 
Which compound has hydrogen bonding?
A NaH
B NH3
C HI
D SiH4
A

B

NH3

21
Q

NO2- ions can be reduced in acidic solution to NO
How many electrons are gained when each NO2- ion is reduced?
A 1
B 2
C 3
D 4

A

A

1

22
Q 
Which is the electron configuration of an atom with only two unpaired electrons?
A 1s2 2s2 2p3
B 1s2 2s2 2p4
C 1s2 2s2 2p6 3s2 3p5
D 1s2 2s2 2p6 3s2 3p6 4s1 3d5
A

B

1s2 2s2 2p4

23
Q 
Which represents the correct order of increasing radius of the ions?
A F– O2– Li+ Be2+
B Li+ Be2+ O2– F–
C Be2+ Li+ F– O2–
D O2– F– Li+ Be2+
A

C

C Be2+ Li+ F– O2–

24
Q 
Which compound contains a co-ordinate bond?
A HF
B NH3
C CHCl3
D NH4Cl
A

D

NH4Cl

25
Q 
Which property increases down Group 7?
A ability to oxidise a given reducing agent
B boiling point
C electronegativity
D first ionisation energy
A

B

Boiling point

26
Q 
Which of these elements has the highest melting point?
A Argon
B Chlorine
C Silicon
D Sulfur
A

C

Silicon

27
Q

Which statement is not always correct for a reaction at equilibrium?
reactants ⇌ products
A The concentrations of the reactants and products are equal.
B The equilibrium can be achieved starting from the reactants.
C The equilibrium can be achieved starting from the products.
D The rate of the forward reaction is equal to the rate of the
reverse reaction.

A

A

The concentrations of the reactants and products are equal.

28
Q 
Which compound contains chlorine in an oxidation state of +1?
A Cl2O
B KClO3
C ClF3
D CCl4
A

A

Cl2O

29
Q 
Which equation shows a redox reaction that does not occur?
A Br2(aq) + 2KI(aq) → I2(aq) + 2KBr(aq)
B Cl2(g) + 2KI(aq) → I2(aq) + 2KCl(aq)
C Cl2(g) + 2KBr(aq) → Br2(aq) + 2KCl(aq)
D I2(aq) + 2KBr(aq) → Br2(aq) + 2KI(aq)
A 
D
D I2(aq) + 2KBr(aq) → Br2(aq) + 2KI(aq)
30
Q 
Which molecule has a permanent dipole?
A CF4
B PCl5
C CO2
D Cl2O
A

D

Cl2O

A level Chemistry Past Papers (1 decks)

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