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A level Chemistry 2 > Hard questions from past papers > Flashcards

Hard questions from past papers Flashcards

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1
Q

What does .XH2O represent in the formula Al2(SO4)3(aq).xH2O

A

Number of water of crystallisation

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2
Q

Suggest formula of the ion responsible for bleaching when chlorine reactions with NaOH (aq)

A

ClO-

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3
Q

Why is Na3PO4 described as a salt of H3PO4

A

Hydrogen ions are replaced by the sodium ions

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4
Q

Why is it unnecessary to refer to carbon as either diamond or graphite in a table pf 1st ionisation energies

A

Diamond and graphite form gaseous atoms of carbon when they are ionised

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5
Q

Particles between which the force of the bond is acting in fluorine

A

Between molecules

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6
Q

Suggest formulae of the ions present in H4N2O3

A

NH+ NO3-

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7
Q

Describe and explain the electrical conductivity of Na

A

Sodium conducts in the solid and molten states. Sodium has delocalised electrons (in both solid and
liquid state)

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8
Q

State conditions for the reaction of aqueous sodium hydroxide and chlorine

A

Cold and dilute NaOH

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9
Q

How to find formula of solid product formed after SrCl2.6H2O is heated and water is lost

A
  1. Find moles of SrCl2.6H2O
  2. Find moles of water lost
  3. Divide moles of water lost by moles of SrCl.6H2O to find moles of water lost from 1 mol of SrCl2.6H2O
  4. Take this number away from the number of moles of water to start with (6) to get your final formula
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10
Q

Write reaction between Barium nitride and water to form an alkaline solution and an alkaline gas

A

Ba3N2 + 6H2O → 3Ba (OH)2 + 2NH3

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11
Q

Draw dot and cross diagram of BaO2 which contains Barium and peroxide ions

A

Ba 2+ in one bracket

2 oxygen bonded together with one electron from each Ba on each oxygen. This is in brackets with a 2- round the side.

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12
Q

State one type of a biodegradeable alternative to CFCs

A

HCFCs

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13
Q

Give an everyday use for infrared spectroscopy

A

Breathalysers and to monitor air pollution

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14
Q

Describe and explain using equations how the concentration of ozone in the stratosphere is maintained

A

O3→02 +O
O + O2→ O3
Rate of ozone decomposition equals rate of ozone formation

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15
Q

Cyclopropane undergoes an addition reaction with bromine in the absence of UV. Suggest the structure of the organic product produced

A

1,3-dibromopropane

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16
Q

Suggest one advantage of adding cyclohexane to petrol

A

It will burn more efficiently

17
Q

Suggest a reactant other than a different acid that could be used to imporve the atom economy of making 1-bromobutane

A

Add NaBr directly instead of KBr and H2SO4

18
Q

Suggest one other method of CCS apart from reacting CO2 with a metal oxide

A
  1. Store deep in the oceans
19
Q

How do you get from a alkene to an alcohol

A

Add KOH (aq)

20
Q

Suggest 2 properties that make CF2CL2 suitable for use as an aerosol

A
  1. Low reactivity/ will not burn
  2. Volatile/ low boiling point
  3. Non poisonous
21
Q

What happens to molecules when infrared radiation is absorbed

A

The bonds vibrate

22
Q

What is the general formula of the homologous series that has CH2=CHCH2Br as a member

A

CnH2n-1Br

23
Q

Suggest reasons for the difference in the calculated value for deltaHc and the value from data books

A
  1. Heat loss
  2. Incomplete combustion
  3. Non- standard conditions
  4. evaporation of alcohol/water
  5. Specific heat capacity of beaker
24
Q

Write the state of hexane

A

liquid

25
Q

Why is it difficult to determine the standard enthalpy change of formation of hexane directly

A
  1. Many different hydrocarbons would be produced

2. activation energy too high/ reaction too slow/ they don’t react

26
Q

State two reasons why there is still concern about ozone depletion

A
  1. CFCs take many years to reach the ozone
  2. CFCs are still being used
  3. There are other ozone depleting substances
27
Q

Outline 2 ways waste polymers are processed usefully

A
  1. Separation into tyres and recycling
  2. Combustion for energy generation
  3. Used for cracking or feedstock for plastics or chemicals
28
Q

Suggest with the aid of an equation, how NO is formed within an aeroplane engine

A

N2 + O2→ 2NO

29
Q

Explain the advantages of the manufacture of H2O2 from hydrogen and oxygen, compared to using BaO2 with H2SO4 and forming BaSO4

A
  1. Oxygen comes from the air
  2. No poisonous materials formed
  3. No waste products formed
30
Q

Explain why some reactions are exothermic

A
  1. Bond breaking absorbs energy and bond making releases energy
  2. More energy is released than absorbed
31
Q

Do graphs showing change in temp and levels of CO2 provide reliable evidence that an increase in atmospheric carbon dioxide concentration will result in global warming

A
  1. There are times when there is a high concentration of CO2 and the temperature is also high
  2. It is impossible to measure with certainty the temperature years ago
  3. There are other gases that may cause a greenhouse affect
  4. There are very few anomalous results
32
Q

Suggest why some scientists are more concerned about CO2 as a greenhouse gas than methane

A
  1. Greater concentration of CO2

2. C=O absorbs carbon dioxide more readily than CH

33
Q

Write equations or reaction of chlorine with dilute and concentrated NaOH

A
  1. Dilute: Cl2 + 2NaOH → NaClO + NaCl + H2O

2. Concentrated: 3Cl2 + 6NaOH → NaClO3 + 5NaCl +3H2O

34
Q

Describe one difference you might observe if strontium instead of magnesium reacted with dilute HCl

A
  1. Quicker/ more vigorous/ gets hotter
35
Q

What apparatus should a student use to measure acid solution to 250cm3

A

Volumetric flask

36
Q

What apparatus should be used to measure the 25cm3 of acid

A

Pipette

37
Q

Suggest what the student could do to reduce the effect of any random error in a titration

A
  1. Repeat until two results are concordant

2. Calculate mean titre from the concordant results

A level Chemistry 2 (22 decks)

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