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Definitions Flashcards

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1
Q

CIS/TRANS ISOMERISM

A

A special case of E/Z isomerism in which two of the substituent groups attached to each carbon atom of the C=C group are the same (these are often, but not always, a H atom).

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2
Q

REDUCING AGENT

A

A reagent which reduces another species (and is itself oxidised) by losing electrons.

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3
Q

PRECIPITATE

A

An insoluble solid formed when two solutions are mixed together.

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4
Q

DYNAMIC EQUILIBRIUM

A

Exists in a closed system when the rate of ten forward reaction is equal to the rate of the reverse reaction and the concentrations of reactants and products do not change.

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5
Q

AVERAGE BOND ENTHALPY

A

The average enthalpy change for the breaking of one mole of bonds in gaseous molecules (by homolytic fission).

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6
Q

BASE (BRONSTED-LOWRY)

A

Proton acceptor.

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7
Q

ATOMIC NUMBER

A

The number of protons in the nucleus of an atom.

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8
Q

Le CHATELIER’S PRINCIPAL

A

When a system in dynamic equilibrium is subjected to a change, the position of equilibrium will shift to minimise the effects of the change.

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9
Q

STRONG ACID

A

A proton donor which completely dissociates into its ions in solution.

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10
Q

OXIDISING AGENT

A

A reagent which oxidises another species (and is itself reduced) by gaining electrons.

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11
Q

ENTHALPY CHANGE

A

The amount of heat released (or absorbed) by a chemical reaction, carried out at constant pressure. Units: kJ mol-1.

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12
Q

PI () BOND

A

Double sideways overlap of adjacent p orbitals above and below the plane of the bonding atoms, with restricted rotation of the bond.

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13
Q

METALLIC BONDING

A

The strong electrostatic attraction between metal cations (positive ions) and delocalised electrons (in a giant metallic lattice structure).

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14
Q

CATALYST

A

Increases the rate of a reaction without being used up by the overall reaction. It allows the reaction to proceed via a different route with lower activation energy.

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15
Q

OXIDATION

A

The loss of electrons / an increase in oxidation number (state).

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16
Q

RETENTION FACTOR

A

Distance moved by the component (from base line)/distance moved by solvent front (from base line).

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17
Q

OXIDATION REACTION

A

A reaction where oxygen is added and/ or hydrogen is removed from a molecule.

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18
Q

STRUCTURAL ISOMERS

A

Compounds with the same molecular formula but different structural formulae.

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19
Q

ALICYCLIC

A

An aliphatic compound arranged in non-aromatic rings with or without side chains.

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20
Q

STANDARD ENTHALPY CHANGE OF HYDRATION

A

The enthalpy change that takes place when one mole of isolated gaseous ions is dissolved in water forming one mole of aqueous ions under standard conditions.

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21
Q

(GIBBS) FREE ENERGY CHANGE

A

The balance between the enthalpy change (ΔH), the entropy change (ΔS) and temperature (T) for a process. ΔG = ΔH - TΔS ΔG, determines the feasibility of a reaction: a reaction is feasible if ΔG < 0.

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22
Q

SALT

A

A compound produced when a H+ ion from an acid is replaced by a metal ion or another positive ion, such as the ammonium ion.

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23
Q

CHROMATOGRAPHY

A

An analytical technique that separates components in a mixture between a mobile phase and a stationary phase.

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24
Q

ANHYDROUS

A

Describes a substance that does not contain water.

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25
Q

DEGRADABLE POLYMER

A

A polymer that breaks down into smaller fragments when exposed to light, heat or moisture.

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26
Q

IONIC PRODUCT OF WATER

A

The dissociation of water: H2O H+ + OH- Kw = [H+] [OH-] units = mol2dm-6 At 250C Kw = 1.00 x 10-14 mol2dm-6.

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27
Q

HYDRATED

A

When water of crystallisation is present in a crystal compound.

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28
Q

MOBILE PHASE

A

The phase which moves in chromatography; a liquid (TLC) or a gas (GC).

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29
Q

MOLECULAR FORMULA

A

The actual number and type of atoms of each element in a molecule.

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30
Q

DISPLACEMENT REACTION

A

A reaction in which a more reactive element (halogen) displaces a less reactive element (halogen) from an aqueous solution of its halide ions.

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31
Q

PERIODICITY

A

The repeating pattern of chemical and physical properties across different periods.

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32
Q

SIGMA () BOND

A

Single end-on (axial) overlap of orbitals directly between bonding atoms, allowing free rotation of the bond.

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33
Q

COVALENT BOND

A

The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms.

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34
Q

RETENTION TIME

A

The time taken from a component to pass from the column inlet to the detector (in GC).

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35
Q

STANDARD CELL POTENTIAL

A

Eθcell = Eθreduction - Eθoxidation For a reaction to be feasible, the species undergoing reduction must have the more positive Eθ value: Eθcell > 0.

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36
Q

ACID (BRONSTED-LOWRY)

A

Proton donor.

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37
Q

MOLE FRACTION

A

Number of moles of A/total number of moles in gas mixture.

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38
Q

ALIPHATIC

A

A compound containing carbon and hydrogen joined together in straight chains, branched chains or non-aromatic rings.

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39
Q

STANDARD ENTHALPY CHANGE OF SOLUTION

A

The enthalpy change when one mole of a compound is completely dissolved in water under standard conditions.

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40
Q

ENDOTHERMIC REACTION

A

A reaction where heat energy is absorbed from the surroundings. (ΔH is positive).

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41
Q

CURLY ARROW

A

The movement of an electron pair, showing either heterolytic fission or formation of a covalent bond.

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42
Q

MOLE

A

The amount of substance containing as many particles as there are carbon atoms in exactly 12g of Carbon-12.

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43
Q

STEREOISOMER

A

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

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44
Q

DEHYDRATION REACTION

A

A reaction where a H2O molecule is removed from a saturated molecule to form an unsaturated molecule.

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45
Q

RATE OF REACTION

A

The change in concentration of a reactant or product per unit time.

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46
Q

EXOTHERMIC REACTION

A

A reaction where heat energy is released to the surroundings. (ΔH is negative).

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47
Q

OPTICAL ISOMERISM

A

An example of stereoisomerism in which there is a pair of non-superimposable mirror images of one another, about a chiral centre.

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48
Q

HOMOLYTIC FISSION

A

The breaking of a covalent bond where each bonding atom receives one electron from the bonding pair of electrons, forming two radicals.

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49
Q

RELATIVE ISOTOPIC MASS

A

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

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50
Q

IONIC BOND

A

The electrostatic attraction between positive and negative (oppositely charged) ions.

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51
Q

STRUCTURAL FORMULA

A

The minimum detail required to show the arrangement of atoms in a molecule, e.g. for butane: CH3CH2CH2CH3 or CH3(CH2)2CH3.

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52
Q

DISPLAYED FORMULA

A

shows the relative positioning of atoms and the bonds between them, e.g. for ethanol:

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53
Q

AROMATIC

A

A compound containing a benzene ring.

54
Q

LIGAND

A

A molecule or ion that can donate a pair of electrons with the transition metal ion to form a coordinate bond.

55
Q

COORDINATION NUMBER

A

The total number of coordinate bonds formed between a central metal ion and its ligands.

56
Q

MOLAR GAS VOLUME

A

The gas volume per mole of a substance. This is 24.0 dm3mol-1 at room temperature and pressure (RTP).

57
Q

-AMINO ACID

A

Molecule with general formula RCH(NH2)COOH.

58
Q

HYDROCARBON

A

Compounds composed of only carbon and hydrogen.

59
Q

DATIVE (CO-ORDINATE BOND)

A

The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms, where only one of the atoms supplies both the electrons shared.

60
Q

CONDENSATION POLYMERISATION

A

The joining of monomers with the elimination of a small molecule such as water.

61
Q

ALKALI

A

A base that dissolves in water and releases OH- ions in aqueous solution.

62
Q

WATER OF CRYSTALLISATION

A

Water molecules that are bonded into a crystalline structure of a compound.

63
Q

REDUCTION

A

The gain of electrons / a decrease in oxidation number (state).

64
Q

AVOGADRO’S CONSTANT

A

The number of particles per mole of a substance (6.02 x 1023 mol-1).

65
Q

STANDARD STATES

A

Physical states under standard conditions.

66
Q

STATIONARY PHASE

A

The phase that does not move in chromatography; a solid (TLC) or a liquid on a solid support (GC).

67
Q

MASS NUMBER

A

The total number of protons and neutrons in the nucleus of an atom.

68
Q

UNSATURATED

A

Containing at least one multiple carbon-carbon bond, including C=C, C=C and aromatic rings.

69
Q

d-BLOCK ELEMENT

A

Element which has the highest energy electron in a d sub-shell (or d orbital).

70
Q

LIGAND SUBSTITUTION

A

A reaction in which one ligand in a complex ion is replaced by another ligand.

71
Q

TRANSITION ELEMENT

A

d block element that has an ion with an incomplete d sub-shell.

72
Q

HETEROLYTIC FISSION

A

The breaking of a covalent bond where one bonding atom receives both electrons from the bonding pair of electrons, forming two oppositely charged ions.

73
Q

DISTILLATION

A

The technique of heating a liquid to create vapour which is collected when cooled and condensed, separate from the original liquid. (often used to separate liquids based on their boiling points).

74
Q

SKELETAL FORMULA

A

The simplified organic formula, shown by ‘hiding’ every C atom and any H atom which is directly attached to a C atom, leaving just the carbon skeleton and any functional groups. e.g. for butan-2-ol:

75
Q

VOLATILITY

A

The ease with which a liquid turns into a gas.

76
Q

CONJUGATE ACID-BASE PAIR

A

A pair of two species that transform into each other by the gain or loss of a proton (H+).

77
Q

RELATIVE ATOMIC MASS

A

The weighted mean mass of an atom of an element compared with one-twelfth of the mass of an atom of carbon-12.

78
Q

RATE EQUATION

A

Gives the relationship between the rate of reaction and the concentration of the reactants raised to the powers of their orders. Example, for the reaction: A + B products Rate equation: rate = k [A]m [B]n.

79
Q

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.

80
Q

SATURATED

A

Containing single carbon-carbon bonds only.

81
Q

ATOMIC ORBITAL

A

A region around the nucleus that can hold up to two electrons, with opposite spins.

82
Q

HESS’ LAW

A

The enthalpy change of a reaction depends only on the initial and final states and is independent of the route taken.

83
Q

ELECTRON PAIR REPULSION THEORY

A

• The shape of simple covalent molecules and ions are determined by the number & type of electron pairs around the central atom.
• Electron pairs repel one another as far apart as possible • Lone pairs of electrons repel more strongly than bond pairs of electrons.

84
Q

FUNCTIONAL GROUP

A

A group of atoms within a molecule responsible for the characteristic reactions of a compound.

85
Q

DISPROPORTIONATION

A

A reaction in which the same element is both oxidised and reduced.

86
Q

CONDENSATION REACTION

A

A reaction where an H2O molecule is lost when two molecules join together.

87
Q

BUFFER SOLUTION

A

A system that minimises pH changes on addition of small amounts of an acid or a base.

88
Q

OXIDATION NUMBER

A

A measure of the number of electrons that an atom uses to bond with atoms of another element.

89
Q

LATTICE ENTHALPY

A

The enthalpy change when one mole of an ionic compound is formed from its gaseous ions under standard conditions

90
Q

ADDITION REACTION

A

A reaction where a group is added across a double bond of an unsaturated molecule to make a saturated molecule (one product).

91
Q

RATE-DETERMINING STEP

A

The slowest step of a reaction mechanism of a multi-step reaction.

92
Q

HOMOLOGOUS SERIES

A

A series of organic compounds with the same functional group but with each successive member differing by CH2.

93
Q

STANDARD CONDITIONS

A

• Temperature = 25 oC (298 K)
• Pressure of gases = 1 atm (100 kPa)
• Concentration of (aq) solutions = 1.00 moldm-3

94
Q

STANDARD ENTHALPY CHANGE OF FORMATION

A

The enthalpy change that takes place when one mole of a compound is formed from its constituent elements in their standard states under standard conditions.

95
Q

STANDARD ENTHALPY OF COMBUSTION

A

The enthalpy change when 1 mole of a substance is completely burned in oxygen under standard conditions.

96
Q

SOLUTION

A

A homogeneous mixture composed of two or more substances. A solution consists of a solute and a solvent. The solute is the substance that is dissolved in the solvent. These are usually transparent.

97
Q

CHIRAL CENTRE (carbon)

A

A carbon atom with four different groups attached.

98
Q

SUCCESSIVE IONISATION ENERGY

A

A measure of the energy required to remove each electron in turn.

99
Q

COMPLEX ION

A

A transition metal ion bonded to one or more ligands by coordinate bonds (dative covalent bonds).

100
Q

STANDARD ELECTRODE (REDOX) POTENTIAL

A

The e.m.f. (electromotive force / voltage) of a half cell compared with a standard.

101
Q

ELECTRONEGATIVITY

A

The ability of an atom to attract the bonding electrons towards itself in a covalent bond.

102
Q

HEAT UNDER REFLUX

A

The continuous boiling and condensing of a liquid (in a condenser) preventing loss of volatile liquids from a heated reaction vessel.

103
Q

HYDROLYSIS REACTION

A

A chemical reaction involving water or an aqueous solution, which causes the breaking of a bond, splitting a reactant molecule into two products.

104
Q

ACTIVATION ENERGY

A

The minimum energy required for a reaction to take place, by the breaking of bonds in the reactants.

105
Q

HETEROGENEOUS CATALYST

A

Catalyst has a different physical state from the reactants (frequently, reactants are gases while the catalyst is a solid).

106
Q

ALKYL GROUP

A

Of formula CnH2n+1.

107
Q

HALF-LIFE

A

The time taken for the concentration of a reactant to fall to half of its original concentration. (For a first order reaction, half-life is constant).

108
Q

BIDENTATE LIGAND

A

A ligand which can donate two lone pairs of electrons to the central metal ion to form two coordinate bonds.

109
Q

HOMOGENEOUS CATALYST

A

Catalyst is in the same physical state as the reactants (frequently, the aqueous or gaseous state).

110
Q

RATE CONSTANT

A

: ‘k’ in the rate equation: the larger the value of k, the faster the reaction. k is constant at a constant temperature and increases with temperature (Arrhenius).

111
Q

ISOTOPES

A

Atoms of the same element with different numbers of neutrons.

112
Q

PARTIAL PRESSURE

A

mole fraction of A x total pressure P.

113
Q

GENERAL FORMULA

A

The simplest algebraic formula for any member of a homologous series, e.g. for an alkane: CnH2n+2.

114
Q

FUEL CELL

A

A cell which uses the energy from the reaction of a fuel with oxygen to create a voltage.

115
Q

ELIMINATION REACTION

A

A reaction where an atom or group is removed from a molecule to make an unsaturated molecule.

116
Q

EMPIRICAL FORMULA

A

The simplest whole number ratio of atoms of each element present in a compound.

117
Q

REDOX

A

A reaction where both oxidation and reduction take place.

118
Q

E/Z ISOMERISM

A

An example of stereoisomerism in which there is restricted rotation about a C=C double bond, and each carbon atom of the C=C double bond has two different groups attached to it.

119
Q

STANDARD ENTHALPY OF NEUTRALISATION

A

The energy change that accompanies the neutralisation of an aqueous acid by an aqueous base to form one mole of H2O(l), under standard conditions.

120
Q

NUCLEOPHILE

A

An electron pair donor.

121
Q

MOLAR MASS

A

The mass in grams of one mole of a substance.

122
Q

STANDARD ENTHALPY CHANGE OF REACTION

A

The enthalpy change that accompanies a reaction in the molar quantities expressed in a chemical equation under standard conditions, all reactants and products being in their standard states.

123
Q

RADICAL

A

Species with an unpaired electron (e.g. Cl.)

124
Q

ENTROPY

A

A measure of the dispersal of energy in a system which is greater, the more disordered a system.

125
Q

ORDER

A

How the concentration of a reactant affects the rate of the reaction. In the rate equation above, Order with respect to A = m Order with respect to B = n Overall order = m + n.

126
Q

EQUILIBRIUM CONSTANT

A

For an equilibrium reaction: A + B C + D Kc = [C]c [D]d Kp = p(C)c x p(D)d [A]a [B]b p(A)a x p(B)b [ ] = equilibrium concentrations p = partial pressures (for gases).

127
Q

ACID DISSOCIATION CONSTANT

A

For a weak acid: HA H+ + A- Ka = [H+] [A-] units = moldm-3 [HA] and pKa = - log Ka.

128
Q

BIODEGRADABLE POLYMER

A

A polymer that breaks down completely into CO2 and H2O.

129
Q

ELECTROPHOLE

A

An electron pair acceptor.

130
Q

p-BLOCK ELEMENT

A

Element which has the highest energy electron in a p sub-shell (or p orbital) (Applies to any element; s-, p-, d- or f-block).

131
Q

WEAK ACID

A

A proton donor which partially dissociates into its ions in solution. pH pH = - log [H+] and [H+] = 10-pH.

132
Q

SUBSTITUTION REACTION

A

A reaction where an atom or group in a molecule is replaced by another atom or group.

Chemistry (40 decks)

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