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A level Chemistry > Exam Qs > Flashcards

Exam Qs Flashcards

1
Q

What is meant by the term structural isomers? (1)

A

compounds/ molecules having the same general formula but different structural formulae

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2
Q

alkane with the lowest BP has the …………….. branching

A

most

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3
Q

catalyst required to prepare butan-2-ol from butene

A

H3PO4

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4
Q

What is meant by the term average bond enthalpy? (2)

A

Average enthalpy change when one mole of gaseous covalent bonds is broken

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5
Q

What properties make CFCs good for use as aerosols?

A
  • low reactivity/ will not burn/ non-flammable
  • volatile/ low BP
  • non-toxic/ non-poisonous
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6
Q

Explain ‘Life on Earth benefits from the presence of an ozone layer’

A

Ozone absorbs UV (radiation)

UV at Earth’s surface is reduced

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7
Q

How is the concentration of ozone is maintained in the ozone layer?

A

O3 ⇌ O2 + O

Formation and breakdown of ozone is in equilibrium

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8
Q

Show how CF2Cl2 produces radicals which catalyse the breakdown of ozone

A

Production of radicals:
CF2Cl2 → •Cl+ CF2Cl

Breakdown of O3:
•Cl + O3 → ClO• + O2
ClO• + O → Cl• + O2

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9
Q

What happens to molecules when IR radiation is absorbed?

A

bond vibrates (more)
/ bends
/ stretches

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10
Q

What is meant by the term homologous series? (2)

A

series of organic compounds with the same functional group 

and with each successive member differing by CH2

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11
Q

What does a curly arrow represent in mechanisms?

A

Movement of an electron pair

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12
Q

What is meant by the term nucleophile?

A

Electron pair donor

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13
Q

alkene -> alkane

reagents and conditions

A

H2

Ni catalyst

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14
Q

Suggest reasons why radical substitution produces a mixture of organic products (2)

A 
Further substitution
or
Produces different termination products
or
More than one termination step

Substitution at different positions along chain 

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15
Q

The calculated value of ΔHc from an experiment where a spirit burner is used to heat a beaker of water is different from the value obtained from data books.

Suggest reasons for the difference

A 
Heat loss
Incomplete combustion
Non-standard conditions
Evaporation of alcohol/water
Specific heat capacity of beaker/apparatus
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16
Q

Why does the cyclopentane have a higher BP than cyclopropane? (2)

A

More carbons (in ring) OR more (surface area of) contact

AND more london forces OR stronger london forces 
More energy needed to break the intermolecular forces 

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17
Q

Suggest one advantage of adding cyclohexane to hexane in petrol.

A

cyclohexane will burn more efficiently

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18
Q

Explain what is meant by the term stereoisomers.

A

(Compounds with the) same structural formula but a different arrangement (of atoms) in space

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19
Q

Explain why the initiation step in radical substitution c fission.

A

the breaking of an X-X bond and the formation of two radicals

one electron from from the bonding pair goes to each atom

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20
Q

what are 3 features of a dynamic equilibrium?

A
  • closed system needed
  • rate of forward reaction = rate of reverse reaction
  • relative conc of reactants and products does not change
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21
Q

standard enthalpy change of formation (3)

A

enthalpy change when one mole of a compound is formed from its elements under standard conditions (298K, 100kPa)

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22
Q

How is a salt formed in a reaction?

A

A hydrogen ion of an acid has been replaced by a metal ion

23
Q

Describe what is meant by the term ionic lattice, in terms of type and arrangement of particles present

A

Regular repeating pattern

Of oppositely charged ions

24
Q

Explain what is meant by the term base

A

A substance which readily accepts H+ ions from an acid

25
Q

Explain what is meant by the term alkali

A

Species which releases OH- ions into aqueous solution

26
Q

Explain what is meant by first ionisation energy

A

The energy required to remove one electron from each atom in one mole of gaseous atoms to form one mole of gaseous 1+ ions

27
Q

Describe and explain the trend in first IE across P2

A

First IE increases

  • similar shielding
  • atomic radius decreases
  • nuclear charge increases

-> outermost electron experiences greater electrostatic attraction to nucleus so requires more energy to remove

28
Q

Describe and explain the trend in first IE down a group

A
  • first IE decreases
  • outer e experiences greater electron shielding
  • increasing atomic radius
  • despite increased nuclear charge

-> outer e experiences less attraction to nucleus so is easier to remove

29
Q

Explain what is meant by isotopes

A

Atoms of the same element with different no. Neutrons and different masses

30
Q

Explain what is meant by relative isotopic mass

A

The mass of an isotope compared with 1/12th the mass of an atom of C-12

31
Q

Explain what is meant by relative atomic mass

A

The weighted mean mass of an atom compared with 1/12th the mass of an atom of C-12

32
Q

Explain what is meant by the term orbital

A

Region around the nucleus that can hold up to two electrons with opposite spins

33
Q

Sequence of tests for unknown salts

A
  • carbonate
  • sulfate
  • halide
  • NH4+
34
Q

Describe the carbonate ion test

A

Add dilute nitric acid

Effervescence and gas produced turns limewater cloudy/milky

35
Q

Describe the sulfate ion test

A

Barium chloride solution

White precipitate is barium sulfate

36
Q

Describe the test for chloride ions

A

Add aqueous AgNO3
White precip of AgCl
Add dilute NH3
Dissolves

37
Q

Describe the test for bromide ions

A

Add aq AgNO3
Cream precip of AgBr
Add dilute NH3 - doesn’t dissolve
Add conc NH3 - does dissolve

38
Q

Describe the test for iodide ions

A

Add aq AgNO3
Yellow precip of AgI
Add conc NH3 - doesn’t dissolve

39
Q

Describe test for NH4+

A

Add NaOH and warm
Pungent smell
Damp red litmus paper turns blue

40
Q

Define an acid

A

A species which releases H+ ions in aqueous solution

41
Q

Define a base

A

A compound that neutralises an acid to form a salt.

Proton acceptor

42
Q

Define an alkali

A

a species which releases OH- ions in aqueous solution

43
Q

Neutralisation is the…

A

reaction of H+ and OH- to form H20

44
Q

Why is the reaction between copper(II) oxide and Hal slow at room temperature?

A

high activation energy because ions have to be separated from the solid before they can react

45
Q

What observations do you make when copper(II) carbonate is added to HCl?

A

Green solid added to colourless solution

Solid disappears, effervescence and the formation of a blue/green solution

46
Q

why is calcium nitrate an example of a salt?

A

it is formed when H+ ions from an acid are replaced by calcium ions (Ca2+)

47
Q

explain how to OH- ion in calcium hydroxide acts as a base when it neutralises dilute nitric acid

A

the OH- ion accepts an H+ ion from HNO3 to form H2O

48
Q

state one use of calcium hydroxide in agriculture and suggest why the amount of calcium hydroxide used should not be excessive (2)

A
  • neutralise acidic soils

- Excess will result in soils becoming too alkaline (to sustain crop growth)

49
Q

why does bp of the halogens increase down the group?

A

van der Waals’ forces OR induced dipole interactions
Additional Guidance
number of electrons increases
Down the group, intermolecular forces / van der Waals’ forces increase
OR
Down the group, more energy needed to break intermolecular / van der Waals’ forces

50
Q

state one advantage and one disadvantage of using chlorine in water treatment

A

Advantage
removes or kills bacteria OR kills germs OR
kills micro-organisms OR make it safe to drink OR sterilises water OR disinfects water

Disadvantage
it is toxic OR poisonous OR could form chlorinated hydrocarbons 
ALLOW forms carcinogens OR forms toxins IGNORE harmful

51
Q

in terms of bond breaking and forming, explain why a reaction is exothermic

A

bond breaking absorbs energy and bond forming releases energy

more energy is released than absorbed

so exothermic

52
Q

describe how chemists can reduce environmental damage from disposal of polymers

A

Incineration to produce energy OR combustion to produce energy 
Sorting and recycling OR sorting and remoulding  Cracked (to give monomers) OR as an organic feedstock

53
Q

NUCLEOPHILE

A

It is an electron pair donor OR can donate a lone pair 

54
Q

lattice enthalpy

A

(The enthalpy change that accompanies)

the formation of one mole of a(n ionic) compound  from its gaseous ions  (under standard conditions)

A level Chemistry (28 decks)

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