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Edexcel Chemistry A Level > Definitions YR13 > Flashcards

Definitions YR13 Flashcards

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1
Q

What is NMR spectroscopy?

A

An analytical technique that allows the structure of a molecule to be determined by analysing bond and atom environments.

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2
Q

What is an environment (NMR)?

A

The environment of an atom depends on the surrounding atoms and bonds in the molecule.

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3
Q

What are stereoisomers?

A

Molecules that have the same structural formula but a different arrangement of atoms in space (E-Z/optical)

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4
Q

What are optical isomers?

A

Non-superimposable mirror images which rotate the plane of plane-polarised light in an equal amount but opposite directions.

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5
Q

What is plane-polarised light?

A

Light which oscillates in one plane.

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6
Q

What is a polarimeter?

A

Apparatus which can be used to measure the rotation of plane-polarised light.

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7
Q

What is a chiral carbon?

A

A chiral carbon has four different groups bonded to it (chiral centre/asymmetric carbon).

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8
Q

What are enantiomers?

A

Optical isomers of the same molecule

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9
Q

What is a racemic mixture?

A

A racemic mixture (racemate) is a 50-50 mixture of the two enantiomers of an optical isomer, so doesn’t rotate the plane of plane-polarised light as the rotations cancel.

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10
Q

What are carbonyl compounds?

A

Aldehydes or ketones (at A Level). The carbonyl group is C=O.

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11
Q

What are hydrolysis reactions?

A

Reactions in which a compound is split apart in a reaction involving water.

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12
Q

What are condensation reactions?

A

Reactions which join two molecules together via the removal of a small molecule (usually water).

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13
Q

What are condensation polymers?

A

Condensation polymers are produced when monomers join together via condensation reactions. This produces the polymer and a small molecule.

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14
Q

What is a dynamic equilibrium?

A

Where the rates of forwards and backwards reactions are equal, so the relative quantities of reactants and products are unchanging.

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15
Q

What is a closed system?

A

One in which the reactants and products (or anything else) cannot enter of leave

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16
Q

What is Le Chatilier’s principle?

A

This states that if a constraint (new condition) is imposed upon a system, the system will act to counteract that constraint.

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17
Q

What is the equilibrium constant?

A

Symbol Kc or Kp, it is a ratio between the reactants and products at equilibrium. It is constant unless the temperature of the equilibrium system is changed.

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18
Q

What is a homogenous system?

A

One in which all reactants and products are in the same states.

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19
Q

What is a heterogenous system?

A

One in which not all reactants and products are in the same state.

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20
Q

What is the partial pressure of a gas?

A

The pressure it would exert if it alone filled its container. Calculated via mole fraction of gas x total pressure.

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21
Q

What is a Brønsted-Lowry acid?

A

A proton donor.

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22
Q

What is a Brønsted-Lowry base?

A

A proton acceptor.

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23
Q

What is a conjugate acid?

A

Formed when a base accepts a proton.

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24
Q

What is a conjugate base?

A

Formed when an acid donates a proton.

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25
Q

What is a conjugate acid-base pair?

A

A pair of species on opposite sides of an equation which are related, and differ only by their number of protons.

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26
Q

What is monoprotic (monobasic) acid?

A

Can donate one proton per molecule (e.g. HCl).

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27
Q

What is a diprotic (dibasic) acid?

A

Can donate two protons per molecule (e.g. H2SO4).

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28
Q

What is a triprotic (tribasic) acid?

A

Can donate three protons per molecule (e.g. H3PO4).

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29
Q

What is pH?

A

-log[H+]

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30
Q

What are strong acids?

A

Acids which fully ionise (dissociate) to produce H+ ions when in solution in water.

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31
Q

What are weak acids?

A

Acids which partially ionise (dissociate) to produce H+ ions when in solution in water

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32
Q

What is the ionic product of water?

A

Kw = [H+][OH-]

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33
Q

What is the acid dissociation constant?

A

Ka = [H+][A-]/[HA]

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34
Q

What is pKa?

A

-log(Ka)

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35
Q

What is the enthalpy change of neutralisation?

A

The enthalpy change when one mole of water is formed by neutralisation between an acid and a base under standard condition (298K).

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36
Q

What is the equivalence point?

A

The point during a titration at which the reactants have fully reacted (for acid/base, mol H+=mol OH-)

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37
Q

What is the half-equivalence point?

A

The point during a titration where exactly half the reactant in the conical flask has been reacted.

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38
Q

What is a pH curve?

A

A graph drawn of pH (y axis) against volume of acid or alkali added (x axis).

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39
Q

What is the buffer region of a pH curve?

A

The region where pH only changes slightly as acid/alkali is added.

40
Q

What are indicators?

A

Weak acids where the protonated species and the deprotonated salt species have different colours.

41
Q

What is a buffer solution?

A

A mixture of a weak acid and its salty that will resist changes in pH when small amounts of acid or alkali are added.

42
Q

What is the enthalpy of atomisation?

A

The enthalpy change when one mole of gaseous atoms are produces from an element in its standard state under standard conditions.

43
Q

What is the standard enthalpy of solution?

A

The enthalpy change when one mole of a solute dissolves completely in a solvent to form a solution in which the ions are far enough apart not to interact with each other, under standard conditions.

44
Q

What is the enthalpy of hydration?

A

The enthalpy change when water molecules surround one mole of gaseous ions, under standard conditions.

45
Q

What is the first electron affinity?

A

The enthalpy change when one mole of electrons is added to a mole of gaseous atoms to form ions with a 1- charge.

46
Q

What is the second electron affinity?

A

The enthalpy change when a mole of electrons is added to a mole of gaseous 1- ions to form ions with a 2- charge.

47
Q

What is the enthalpy of lattice formation?

A

The enthalpy change when one mole of a solid ionic compound is formed from its gaseous ions.

48
Q

What is the enthalpy of lattice dissociation?

A

The enthalpy change when one mole of a solid ionic compound is dissociated into its gaseous ions.

49
Q

What is entropy (S)?

A

A measure of disorder

50
Q

What is the entropy of a system (Ssystem)?

A

The entropy within a chemical reaction (system).

51
Q

What is the entropy of surroundings (Ssurroundings)?

A

The entropy of the surroundings of a chemical reaction (system).

52
Q

What is the Gibbs free energy?

A

The change is Gibbs energy (deltaG) is used to determine if a reaction is feasible.

53
Q

What is a half-cell/electrode?

A

An equilibrium system consisting of a solid metal in a solution of its own ions.

54
Q

What is the electrode potential (E)?

A

A measure of the equilibrium position for a half-cell/electrode.

55
Q

What is the standard electrode potential?

A

The voltage produced by a half-cell when connected to a standard hydrogen electrode., under standard conditions (298K, 100KPa, all solutions 1 mol dm-3)

56
Q

What is the standard hydrogen electrode?

A

Defined as having an electrode potential of 0.00V - consistst of a platinum electrode over which H2 gas is passed at 100KPa pressure in a solution of 1 mol dam-3 H+ ions, all at 298K.

57
Q

What is an electrochemical cell?

A

Produces a potential difference or electromotive force from a redox reaction. It is constructed from two half-cells with different electrode potentials joined together.

58
Q

What is the electromotive force (emf or Ecell)?

A

A measure of the voltage of an electrochemical cell.

59
Q

What is a salt bridge?

A

An ionic connection between the solutions of two half-cells

60
Q

What is a storage cell?

A

A rechargeable cell.

61
Q

What is a fuel cell?

A

A cell which uses a constant supply of fuel and oxidising agent to produce a voltage via a chemical reaction (without burning the fuel).

62
Q

What is the anode?

A

The electrode where oxidation occurs?

63
Q

What is the cathode?

A

The electrode where reduction occurs.

64
Q

What is a redox titration?

A

A titration in which the concentration of a reducing or oxidising agent is determined via a redox reaction.

65
Q

What does it mean to be amphoteric?

A

A substance is unable to act as an acid or as a base.

66
Q

What is a zwitterion?

A

A molecule containing a positive charge on one group and a negative charge on another.

67
Q

What is the isoelectric point of an amino acid?

A

The point at which the amino acid exists as a zwitterion in aqueous solution.

68
Q

What is a d-block element?

A

An element which has its highest energy electron is a d-subshell

69
Q

What is a transition metal?

A

A metal which forms at least one stable ion with partially filled d orbitals

70
Q

What is a complex ion?

A

Consists of a central transition metal ion surrounded by ions or other molecules (ligands) that form co-ordinate (dative) bonds with it.

71
Q

What is a ligand?

A

A species (ion or molecule) with a lone pair which is able to form co-ordinate bonds with transition metal ions.

72
Q

What is the co-ordination number of a transition metal ion in a complex ion?

A

The number of coordinate bonds accepted by the transition metal ion.

73
Q

What is a monodentate ligand?

A

A species that is only able to form one co-ordinate bond to a transition metal ion.

74
Q

What is a bidentate ligand?

A

A species which can form two coordinate bonds to a transition metal ion.

75
Q

What is a multidentate ligand?

A

A species which can form multiple (2 or more) coordinate binds to a transition metal ion.

76
Q

What is the denticity of a ligand?

A

How many coordinate bonds it can form with a transition metal ion.

77
Q

What is the chelate effect?

A

This occurs when multiple ligands of low denticity exchange for a lower number of ligands of higher denticity.

78
Q

What is a catalyst?

A

It speeds up the rate of reaction by providing an alternative mechanism for a reaction with a lower activation energy (not used up).

79
Q

What are heterogenous catalysts?

A

Catalysts which are in a different phase to the reactants.

80
Q

What are homogenous catalysts?

A

Catalysts which are in the same phase as the reactants.

81
Q

What is adsorption?

A

This is when a substance binds to the surface of another.

82
Q

What is desorption?

A

When an adsorbed substance is released from a surface.

83
Q

What is catalyst poisoning?

A

When some substances (impurities in the reaction mixture), permanently adsorb to the surface of the catalyst, reducing the surface area and number of available active sites on the catalysts.

84
Q

What is autocatalysis?

A

This occurs when a reaction is catalysed by one of its own products.

85
Q

What are aryl (aromatic) compounds?

A

Compounds which contain at least one benzene ring

86
Q

What are alkyl (aliphatic) compounds?

A

Compounds which do not contain a benzene ring

87
Q

What are delocalised electrons?

A

Bonding electrons which are not fixed between two atoms in a bond, but shared between three or more atoms.

88
Q

What is resonance?

A

A way of describing the delocalisation of electrons

89
Q

What is reflux?

A

A technique where a mixture is continuously boiled and condensed, usually via the use of a reflux condenser (vertical).

90
Q

What is distillation?

A

A technique used to separate compounds with different boiling points.

91
Q

What is fractional distillation?

A

Uses a fractionating column to ensure separation of compounds with similar boiling points.

92
Q

What are anti bumping granules?

A

Used to ensure smooth boiling, by providing a nucleation site for bubbles to form during boiling.

93
Q

What is solvent extraction?

A

This involves using a solvent to extract a desired compound from a mixture. The extraction solvent must be immiscible with the original solvent, and the desired compound must be more soluble in the extraction solvent than the original solvent (uses a separating funnel).

94
Q

What are drying agents?

A

Used to absorb water from organic liquids (e.g. anhydrous MgSO4)

95
Q

What is recrystallisation?

A

The process of purifying an organic liquid by dissolving it in the minimum volume of hot solvent needed to produce a saturated solution and then cooling it to cause crystals to form.

Edexcel Chemistry A Level (13 decks)

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