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Definitions Flashcards

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1
Q

Bond Dissociation Energy

A

The enthalpy change that takes place when breaking by homolytic fission

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2
Q

Bronsted-Lowry acid

A

A species that is a proton (H+) donor

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3
Q

Bronsted-Lowry Base

A

A species that is a proton (H+) acceptor.

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4
Q

Buffer solution

A

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

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5
Q

Chiral Carbon

A

A carbon atom attached to four different atoms or groups of atoms

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6
Q

Cis-trans isomerism

A

A special type of E/Z isomerism in which there are two non-hydrogen groups and two hydrogen atoms around the C=C double bond; the cis isomer (Z isomer) has H atoms on each carbon on the same side; the trans isomeric (E isomer) has H atoms on each carbon different sides.

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7
Q

Closed System

A

A system isolated from its surroundings

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8
Q

Dative Covalent Bond

A

A pair of electrons in which the bonded pair has been provided by one of the bonding atoms only.

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9
Q

Disproportionation

A

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

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10
Q

E/Z isomerism

A

A type of stereoisomerism in which different groups attached to eachcarbon of a C=C double bond may be arranged differently in space because of the restricted rotation of the C=C bond.

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11
Q

Electronegativity

A

A measure of the attraction of a bonded atom for the pair of electrons in a covalent bond.

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12
Q

Electrophile

A

An electron pair acceptor. An atom (or group of atoms) which is attracted to an electron-rich centre or atom, where it accepts a pair of electrons to form a new covalent bond.

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13
Q

Empirical Formula

A

The formula that shows the simplest whole-number ratio of atoms of each element present in a compound.

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14
Q

Enthalpy H

A

The heat content that is stored in a chemical system.

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15
Q

Entropy

A

The randomness or dispersal of energy of a system.

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16
Q

First electron affinity

A

The enthalpy change that takes place when one electron is added to each
atom in one mole of gaseous atoms to form one mole of gaseous 1- ions.
e.g. O (g) + e - → O - (g)

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17
Q

First Ionisation Energy

A

The energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions. e.g. Na (g) → Na + (g) + e -

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18
Q

Free energy change
∆G

A

The balance between enthalpy, entropy and temperature for a process given by ∆G = ∆H - T∆S. A process is feasible when ∆G < 0.

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19
Q

Half-Life

A

The time taken for the concentration of a reactant to decrease by half.

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20
Q

Hess’ Law

A

If a reaction can take place by more than one route and the initial and final conditions are the same, the total energy change is the same for each route.

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21
Q

Heterolytic fission

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A

The breaking of a covalent bond with a pair of bonding electrons going to one of the centre; forming a cation (positive ion) and an anion (negative ion)

22
Q

Homolytic fission

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A

The breaking of a covalent bond with one of the bonded electrons going to each atom forming two radicals.

23
Q

Lattice enthalpy

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A

The enthalpy change that accompanies the formation of one mole of an ionic compound from its gaseous ions under standard conditions.
e.g. Na + (g) + Cl - (g) → NaCl (s)

24
Q

Le Chatelier’s
Principle

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A

When a system in dynamic equilibrium is subjected to an external change. The system readjusts itself to minimise the effect of the change and to restore equilibrium.

25
Ligand
A molecule or ion that can donate a pair of electrons to the central metal ion.
26
Mole
The amount of any substance containing as many elementary particles as there are Carbon atoms in exactly 12g of the Carbon-12 isotope, that is 6.02 x 10 23 particles.
27
Nucleophile
An electron pair donor. An atom ( or group of atoms) which is attracted to an electron-deficient centre or atom where it donates a pair of electrons to form a new covalent bond.
28
Order
The power to which the concentration of a reactant is raised in the rate equation
29
Rate-determining step
The slowest step in the reaction mechanism of a multi-step reaction.
30
Relative atomic mass Ar
The weighted mean mass of an atom of an element compared with one- twelfth of the mass of an atom of Carbon-12.
31
Relative formula mass
The weighted mean mass of the formula unit of a compound compared with one-twelfth of the mass of an atom of Carbon-12.
32
Relative isotopic mass
The mass of an atom of an isotope compared with one-twelfth of the mass of an atom of Carbon-12
33
Relative molecular mass
The weighted mean mass of a molecule of a compound compared with one-twelfth of the mass of an atom of Carbon-12
34
Retention time
In gas chromatography, the time taken for a component to pass through the column from the inlet to the detector.
35
Specific heat capacity c
The energy required to raise the temperature of 1g of a substance by 1C
36
Standard conditions
A pressure of 100 kPa (for reactions with gases), 298 K (25 o C) and a concentration of 1 mol dm -3 (for reactions with aqueous solutions).
37
Standard electrode potential Eᶿ
The e. m. f. of a half-cell compared with a standard hydrogen half-cell, measured at 298K with solution concentration of 1 mol dm -3 and a gas pressure of 100kPa
38
Standard enthalpy change of atomisation ∆ at Hᶿ
The enthalpy change that takes place when one mole of gaseous atoms forms from the element in its standard state. e.g. Na (s) → Na (g)
39
Standard enthalpy change of combustion ∆ c Hᶿ
The enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions all reactants and products being in their standard states. e.g. C 2 H 6(g) + 3.5O 2(g) → 2CO 2(g) + 3H2O (l)
40
Standard enthalpy of formation ∆ f Hᶿ
The enthalpy change that takes place when one mole of a compound is formed from its constituent elements in their standard states understandard conditions. e.g. C (s) + O2(g) → CO2(g)
41
Standard enthalpy change of hydration ∆ hyd Hᶿ
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. e.g. Na + (g) → Na (aq)
42
Standard enthalpy change of neutralisation ∆ neut Hᶿ
The enthalpy change that accompanies the reaction of an acid by a base to form one mole of H 2 O (l), under standard conditions, with all reactants and products in their standard states. e.g. ½ H 2 S0 4(aq) + NaOH (aq) → Na 2 SO 4(aq) + H 2 O (l)
43
Standard enthalpy change of reaction ∆ r Hᶿ
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. e.g. Mg (s) + 2HCl (aq) → MgCl 2(aq) + H 2(g)
44
Standard enthalpy change of solution ∆ sol Hᶿ
The enthalpy change when 1 mole of an ionic solid dissolves in water to form an aqueous solution of its ions. e.g. NaCl (s) → NaCl (aq)
45
Standard state
The physical state of a substance under standard conditions of 100 kPa and 298 K.
46
Stoichiometry
The ratio of the amount, in moles, of each substance in a chemical equation (essentially the ratio of the balancing numbers).
47
Complex ions
a central transition metal ion is surrounded by ligands bonded by coordinate bonds
48
monodentate ligand
ligand with only one one pair of electrons e.g H20 NH3 CN- Cl-
49
Coordinate bond
Another name for Dative covalent bond used in transition elements
50
Bidentate ligands
A ligand with 2 pairs of lone electrons

Chemistry (5 decks)

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