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My AS Level Chemistry - OCR A > Core Definitions and Core Knowledge - AS level > Flashcards

Core Definitions and Core Knowledge - AS level Flashcards

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1
Q

Periodicity def

A

A repeated pattern or trend

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2
Q

Relative Atomic mass def

A

The relative atomic mass of an element is the average mass of its atoms, compared to 1/12th the mass of a carbon-12 atom

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3
Q

General formula def

A

formula for a family of compounds. E.g. alkanes‡ CnH2n+2 where n is the number of carbon atoms

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4
Q

Empirical formula def

A

shows the ratio of atoms in a compound. It is the simplest ratio in which atoms combine to form a compound

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5
Q

Molecular formula def

A

tells us how many of each type of atom there are in each molecule of the compound

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6
Q

Skeletal formula def

A

all the hydrogen atoms are removed from carbon chains, leaving just a carbon skeleton with functional groups attached to it

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7
Q

Displayed formula def

A

shows all the bonds in the molecule as individual lines (each line represents a pair of shared electrons)

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8
Q

Structural formula def

A

shows how the various atoms are bonded

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9
Q

Hydrated

A

A crystalline compound containing water molecules

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10
Q

Anhydrous def

A

A substance containing no water molecules

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11
Q

Water of crystallisation def

A

The water molecules bonded into a crystalline structure of a compound

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12
Q

How to improve results of water of crystallisation experiment

A
  • Use a mass balance that calculates to a greater number of decimal places to get a more accurate mass reading
  • Heat mixture until you record a constant mass
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13
Q

What happens if compound in water of crystallisation decomposes further?
How to stop this?

A
  • Anhydrous solid mass at end will be less than it should be

- You could heat it more gently, or take mixture off of heat

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14
Q

First ionisation energy

A

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

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15
Q

Second ionisation energy

A

The energy required to remove one electron from each 1+ ion in one mole of gaseous 1+ ions to produce one mole of gaseous 2+ ions

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16
Q

Atomic number def

A

Number of protons in the nucleus

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17
Q

Orbital def

A

A region within an atom that can hold up to two electrons with opposite spin

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18
Q

What is meant by one mole of substance?

A
  • As many particles as there are carbon atoms in 12g of carbon - 12
  • Or: 6.02x10^23 atoms
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19
Q

How do London Forces arise?

A

-there is an uneven distribution of electrons present in molecule
↳ this creates an instantaneous dipole
-these cause induced dipoles in neighbouring molecules

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20
Q

Trend in boiling points of chlorine, bromine and iodine

A

H

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21
Q

Oxidising agent def

A

A substance that oxidises another substance by attracting its electrons and becoming reduced in the reaction itself(absorbs electrons from other substances)

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22
Q

Reducing agent def

A

A substance that reduces another substance in a reaction but becomes oxidised in the reaction itself(loses electrons, donates them)

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23
Q

Metallic bonding def

A

The electrostatic attraction between between cations and delocalised electrons

24
Q

Covalent bonding def

A

The electrostatic attraction between two atomic nuclei and a shared pair of electrons

25
Q

Ionic bonding def

A

The electrostatic attraction between oppositely charged ions

26
Q

Electronegativity def

A

The ability of an atom to attract a lone pair of electrons

27
Q

Anomalous properties of water

A
  • Adhesion/Surface Tension
  • Cohesion
  • Ice is less dense than water - water molecules are more spread apart by hydrogen bonds
  • High specific heat capacity
  • High latent heat of vaporisation
28
Q

Radical definition

A

A species or element with an unpaired electron

29
Q

What is meant by fractional distillation?

A

The separation of different hydrocarbons from crude oil by distillation due to different boiling points of each fraction

30
Q

Methods for reducing pollution due to plastic/polymer disposal

A
  • Make photodegradable polymers
  • Make biodegradable polymers
  • Combustion of the polymers to produce energy
  • Melt, reshape and remould the polymers for reuse
  • Used in feedstock for plastics and chemicals
  • Use waste polymers in organic feedstock
  • Use waste polymers in cracking
31
Q

Atom economy def

A

(sum of) the molecular masses of the desired product ÷ sum of molecular masses of all reactants x 100 to get a percentage

32
Q

Alkali def

A

A substance that releases OH- ions in solution

33
Q

Acid def

A

A substance that releases H+ ions in solution

34
Q

Standard solution def

A

A solution of known concentration

35
Q

How to prepare a standard solution

A

H

36
Q

Linear shape info

A

Bond angle: 180 Degrees
2 Bonded Pairs
0 Lone pairs

37
Q

Non linear shape info

A

2BP
At least one LP
Bond angle less than 120 Degrees

38
Q

Trigonal planar shape info

A

Bond angle: 120 Degrees

3BP

39
Q

Trigonal bipyramidal shape info

A

Bond angles: 120 and 90 Degrees

5BP

40
Q

Tetrahedral shape info

A

Bond angle: 109.5 Degrees

As long as 4BP and no LP

41
Q

Octahedral shape info

A

Bond angle: 90 Degrees

42
Q

Suggest two reasons why standard enthalpy changes of combustion determined experimentally are less exothermic than the calculated theoretical values.

A
  • Conditions may have been non-standard
  • Heat may have been lost to the surroundings
  • Incomplete combustion(for standard enthalpy of combustion)
43
Q

Bond angle of a molecule with 4BP and 0LP

A

109.5 Degrees

43
Q

Bond angle of a molecule with 3BP and 1LP

A

107 Degrees

44
Q

Bond angle of a molecule with 2BP and 2LP

A

104.5 Degrees

45
Q

Standard Enthalpy Change of Formation def

A

The enthalpy change that takes place when 1 mole of a compound is formed from its
constituent elements.
All products and reactants are in standard states and conditions

46
Q

Standard enthalpy change of combustion def

A

The enthalpy chnage that takes place when 1 mole of a compound reacts with oxygen and is completely burnt.
All products and reactants formed under standard conditions in standard states

47
Q

Standard Enthalpy change of neutralisation def

A

the enthalpy change associated with the formation of one mole of water from a reaction
standard comditions and states

48
Q

Standard enthalpy change of reaction def

A

the enthalpy change associated with a given reaction (in the molar quantities given in the equation)

49
Q

Average bond enthalpy def

A

The average enthalpy change that takes place when breaking one mole of a given type of bond in the molecules of a gaseous species, by heterolytic fission,

50
Q

Are bond enthalpy values positive of negative values?

A

Always positive

As energy is required/taken in to break the bonds

51
Q

Why can enthalpy change of formation not be measured directly?

A
  • Byproducts may be formed

- Activation energy is too high

52
Q

Reflux Def

A

The continuous boiling and condensing of a reaction mixture to ensure the reaction takes place without boiling dry.

53
Q

In Markownikoffs rule, explain why one product formed is in much greater quantity than the other organic product.
(2 Marks)

A

The major product is the most stable carbocation formed

The most stable carbocation is the carbon that is bonded to the most carbon groups/atoms

54
Q

Identify two potential disadvantages of using catalyst in industrial processes

A

Catalysts are expensive
Cost - expensive to remove catalysts from reaction mixture and products
Catalysts could be potentially toxic/harmful to humans

My AS Level Chemistry - OCR A (14 decks)

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