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Chemistry > A2 Chemistry Unit 5 Definitions > Flashcards

A2 Chemistry Unit 5 Definitions Flashcards

To know the definitions for Unit % Chemistry by rote.

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0
Q

D-block element

A

An element where the d sub-shell is the highest energy sub-shell that is occupied

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1
Q

Transition Metal

A

A d-block element that forms one or more stable ions with a partially filled d sub-shell

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2
Q

Ligand

A

Atoms, ions or molecules that can donate a lone pair of electrons to form coordinate bonds to a central transition metal ion

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3
Q

Bidente Ligand

A

Ions or molecules, which donate 2 lone pairs of electrons to form 2 coordinate bonds to a central mental ion

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4
Q

Complex ion

A

A central transition metal ion that is bonded to one or more ligand so by coordinate bonds

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5
Q

Coordination number

A

The total number of coordinate bonds formed between the central metal ion and any ligands

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6
Q

Coordinate bond

A

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

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7
Q

Stereoisomers

A

Species with the same structural formulas but with a different arrangement of atoms in space

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8
Q

Precipitation reaction

A

The formation of a solid formed from a solution during a chemical reaction. Usually formed when two aqueous solutions are mixed together

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9
Q

Ligand substitution

A

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

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10
Q

Oxidation number

A

A measure of the number of electrons that an atom uses to bond with atoms of another element. Oxidation numbers are derives from a set of rules

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11
Q

Oxidation

A

Loss of electrons or an increase in oxidation number

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12
Q

Reduction

A

Gain in electrons or a decrease in oxidation number

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13
Q

Redox reaction

A

A reaction in which both reduction and oxidation takes place

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14
Q

Stability constant (kStab)

A

The equilibrium constant for an equilibrium existing between a transition metal ion surrounded by water ligands and the complex formed when the same ion has undergone a ligand substitution

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15
Q

Rate of reaction

A

The change in the concentration of reactants or products over time

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16
Q

Order of reaction

A

The power to which a concentration is raised in the rate equation

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17
Q

Half-life

A

The time taken for the concentration of the reactants to decrease by half

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18
Q

Rate determining step

A

Defined as the slowest step in a reaction

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19
Q

Dynamic equilibrium

A

The equilibrium that exists in a close system when the rate of the forward reaction is equal to the rate of the reverse reaction

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20
Q

Equilibrium law

A

For the equilibrium:
aA + bB ⇄ cC + dD

Kc= [C]^c [D]^d
————-
[A]^a [B]^b

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21
Q

Homogenous equilibrium

A

An equilibrium in which all the species making up the reactants and products are in the same physical state

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22
Q

Heterogenous equilibrium

A

An equilibrium in which all the species making up the reactants and products are in different physical states

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23
Q

Le Chatelier’s Principle

A

When a system in dynamic equilibrium is subjected to a change toe sister adjusts itself to minimise the effect of the change and to restore equilibrium

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24
Q

Bronzed-Lowry acid

A

A species that is a H+ (or proton) donor

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25
Q

Bronzed-Lowry base

A

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

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26
Q

Alkali

A

A type of base that dissolves hydroxide ions (OH-)

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27
Q

Strong Acid

A

A acid which completely disassociates in solution

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28
Q

Weak acid

A

An acid which only partially disassociates in solution

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29
Q

Monoprotic acid

A

An acid which only releases one H+ ion (proton) per acid molecule

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30
Q

Diprotic acid

A

An acid which releases two H+ ions (protons) per acid molecule

31
Q

Triprotic acid

A

An acid which releases three H+ ions (protons) per acid molecule

33
Q

Conjugate acid

A

A species formed when you add a proton to a base

34
Q

Conjugate base

A

A species formed when you add a proton to an acid

35
Q

Buffer solution

A

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

36
Q

Standard enthalpy of Neutralisation

A

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

37
Q

pH and [H*]

A

pH = -log[H*(aq)]

[H*] = 10^-pH

38
Q

Ka

A

For the acid HA:

Ka = [H*(aq)] [A-(aq)]
———————–
[HA(aq)]

39
Q

pKa

A

pKa = -log(Ka)

40
Q

Ionic Product of Water, Kw

A

Kw = [H*][OH-] = 1.00 x 10^-14 mol^2 dm^-6 at 25°c

41
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 in their standard states

42
Q

Standard enthalpy change of formation

A

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

43
Q

Standard enthalpy change of atomisation

A

the enthalpy change that takes place when one mole of gaseous atoms forms from the element in its standard state.

44
Q

standard enthalpy change of hydration

A

the change that takes place when one mole of isolated gaseous ions is dissolved in water under standard conditions

45
Q

standard enthalpy change of solution

A

the enthalpy change that takes place when one mole of one compound is completely dissolved in water under standard conditions

46
Q

lattice enthalpy

A

the enthalpy change that accompanies the formation of 1 mole of an ionic compound from its gaseous ions under standard conditions

47
Q

1st 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.

48
Q

2nd ionisation energy

A

the energy required to remove one electron from each atom in one mole of gaseous 1* atoms to form one mole of gaseous 2* ions.

49
Q

1st electron affinity

A

the enthalpy change that accompanies the addition of one electron to each atom in one mole of gaseous atoms to form one mole of gaseous 1- ions.

50
Q

2nd electron affinity

A

the enthalpy change that accompanies the addition of one electron to each atom in one mole of gaseous 1- ions to form one mole of gaseous 2- ions.

51
Q

Endothermic reaction

A

a reaction in which the enthalpy of the products is greater than the enthalpy of the reactants, resulting in heat being taken in from the surroundings (ΔH = +ve)

52
Q

Exothermic reaction

A

a reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants resulting in heat loss to the surroundings (ΔH = -ve)

53
Q

Enthalpy

A

the heat content that is stored in a chemical system (ΔH)

54
Q

Entropy

A

the quantitive measure of the degree of disorder in a system

55
Q

Free energy change (ΔG)

A

The balance between enthalpy, entropy and temperature for any given process: ΔG = ΔH - TΔS. A process can take place spontaneously when ΔG<0.

56
Q

Redox reaction

A

A reaction in which both reduction and oxidation take place

57
Q

Reduction

A

Gain of electrons or decrease in oxidation number

58
Q

Oxidation

A

Loss of electrons or increase in oxidation number

59
Q

Oxidation number

A

A measure of the number of electrons that an atom uses to bond with atoms of another element. Oxidation numbers are derived from a set of rules

60
Q

Reducing agent

A

A reagent that reduces, adds electrons to, another species

61
Q

Oxidising agent

A

A reagent that oxidises, takes electrons from, another species

62
Q

Standard electrode potential

A

The e.m.f. of a half cell compared with a standard hydrogen half cell, measured at 298K with solution concentrations of 1moldm^-3 and a gas pressure of 100kPa (1 atmosphere)

63
Q

Half reaction

A

A half reaction shows either the oxidation or the reduction of a species but not both.

64
Q

Fuel cell

A

A fuel cell converts the energy from a reaction of a fuel cell with oxygen into a voltage/electrical energy

65
Q

Electrochemical Cell

A

A type of cell that controls electron transfer to produce electrical energy. They are made up of 2 half-cells

66
Q

Q. Describe the bonding in X compound

A

A. A coordinate bond forms when a lone pair of electrons
donated by the (named) ligand is accepted by the (named)
metal ion.

Note: Any question mentioning aqueous solutions of a
transition metal salt wants you to use the [M(H2O)6]n+
complex of the metal, e.g.
An aqueous solution of nickel(ii) sulfate…….means you
should use [Ni(H2O)6]2+ for the reactions in the question.

67
Q

General Precipitation reaction for complex transition metal compounds:

A

[M(H2O)6]n+ + nOH-  [M(H2O)6-n(OH)n] + nH2O

68
Q

General Ligand substitution reaction for complex transition metal compounds:

A

[M(H2O)6]n+ + 6NH3  [M(NH3)6]n+ + 6H2O

(Except Cu:
[Cu(H2O)6]2+ + 4NH3  [Cu(NH3)4(H2O)2]2+ + 4H2O)
[M(H2O)6]n+ + 4Cl-  [MCl4]n+(-4) + 6H2O

69
Q

Q. Explain why a buffer solution is formed when excess
weak acid, HA, is mixed with aqueous base/alkali and how
the solution controls pH when an acid or alkali is added to it?

A

A.
• The (named) weak acid reacts with the (named) base to
form (named) conjugate base ions.
• Some of the (named) weak acid remains.
• Equilibrium that occurs: HA H+ + A-
• When alkali added – (named) weak acid reacts with
added alkali (or use equations to explain)
• When alkali added – Equilibrium shifts to the right.
• When acid added – (named) conjugate base ions react
with the added acid.
• When acid added – Equilibrium shifts to the left.

70
Q

Q. How can you prove a solution is a weak/strong acid or a weak/strong base with a single pH measurement?

A

A. Measured pH is: 7> pH > 1 (weak acid)
< 1 (strong acid)
7< pH < 12 (weak base)
> 12 (strong base)

71
Q

Q. Label the two conjugate acid-base pairs for the reaction

between HA and B?

A

A.

Acid 1 Base 2 Acid 2 Base 1

72
Q

Explaining why a lattice enthalpy value is larger for

one compound than another use the following phrases:

A

…… has a greater charge than ……
…… has a smaller ionic radius than ……
There is a stronger attraction between …… and …… ions
(Fill the blanks with relevant ions baring in mind that ions of species get smaller as you go right across a period and up a group in the periodic table).

73
Q

Decide and describe the sign of an entropy change

of a reaction use phrases like the following:

A 
ΔS is +ve when there is an increase in disorder due to:
Forms a liquid from a solid
Forms a gas from a liquid
Forms more moles of gas
ΔS is -ve when there is a decrease in disorder due to:
Forms a solid from a liquid
Forms a liquid from a gas
Forms less moles of gas
Electrode potentials
74
Q

Drawing out electrochemical cells:

A

Draw out the two relevant half-cells.
Connect the solid electrodes of each with wires (with a
possible voltmeter).
Connect the solutions of each with a salt bridge (and
label the salt bridge).
The overall reaction that occurs when two half cells are
combined is found as:
The half equation with the most positive Eº value does
the reduction reaction and…
Combining the half equations (and multiplying to
balance the electrons if need be) will give the overall
reaction.
Working out whether a reaction is spontaneous or not:
Combine the two relevant half equations (using the Eº
values for each) to work out the overall equation that
happens.
If this matches the suggested reaction, then the
reaction is feasible/spontaneous. If it doesn’t then the
reaction is not feasible/spontaneous.

75
Q

Q. What is the difference between electrochemical and fuel

cells?

A

A.
Fuel cells convert energy from the reaction of a fuel
with oxygen into electrical energy.
Electrochemical cells generate electrical energy via the
electron transfer between half cells of different
electrode potentials

Chemistry (4 decks)

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