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Chemistry > Physical chemistry defintions > Flashcards

Physical chemistry defintions Flashcards

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1
Q

What does the mass spectrometer give accurate information about?

A

Relative isotopic mass and the relative abundance of isotopes

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2
Q

What can mass spectrometry be used to identify?

A

Elements

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3
Q

What can mass spectrometry be used to determine?

A

Relative molecular mass

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4
Q

What are the 4 stages of mass spectrometry?

A

Vaporisation, acceleration, ionic drift, detection

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5
Q

What is first ionisation energy?

A

The energy needed to remove 1 electron from each atom of an element in 1 mole of gaseous atoms, to form 1 mole of gaseous ions with a +1 charge

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6
Q

What is relative atomic mass (Ar)?

A

The average mass of an atom of an element relative to 1/12 the mass of an atom of carbon-12

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7
Q

What is relative molecular mass (Mr)?

A

The weighted mean mass of a molecule compared with 1/12 of the mass of an atom of carbon-12

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8
Q

What is the ideal gas equation?

A

pV= nRT

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9
Q

What is the empirical formula?

A

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

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10
Q

What is the molecular formula?

A

The actual number of atoms of each element in a compound

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11
Q

Why is a high percentage atom economy important?

A

Provides economic, ethical and environmental advantages for society and for industry of developing chemical processes.

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12
Q

What is Ionic bonding?

A

Between metal and non-metals, electrostatic attraction between oppositely charged ions in a lattice.

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13
Q

What is Covalent bonding?

A

Between non-metals, share a pair of electrons.

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14
Q

What is Co-ordinate/ Dative bonding?

A

Type of covalent bonding in which the shared pair of electrons are both supplied by one atom.

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15
Q

What is Metallic bonding?

A

Between metals, attraction between delocalised electrons and positive ions arranged in a lattice.

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16
Q

What determines the shape of molecules and ions?

A

The number of bonding pairs and lone pairs of electrons, pairs of electrons in outer shell of atoms arrange themselves to be as far apart as possible to minimise repulsion.

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17
Q

Why is lone pair- lone pair repulsion greater than lone pair-bond pair repulsion?

A

Lone pairs of electrons are closer to the central atom than bonding pairs are, their electron charge clouds are more concentrated and wider.

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18
Q

What is the effect of electron pair repulsion on bond angle?

A

The greater the repulsion force between two pairs of electrons, the further apart the two pairs of electrons will be thus a larger bond angle between them.

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19
Q

What is electronegativity?

A

The power of an atom to attract the pair of electrons in a covalent bond.

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20
Q

What causes a polar bond?

A

When the electron distribution in a covalent bond between elements with different electronegativities is unsymmetrical. Eg: bonded with F, O, N, Cl —-> produces a permanent dipole

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21
Q

What are the intermolecular forces?

A

induced dipole-dipole (van der Waals), permanent dipole-dipole, hydrogen bonding

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22
Q

What do intermolecular forces affect?

A

The melting points and boiling points

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23
Q

What is an exothermic reaction?

A

When a reaction releases energy, enthalpy change is negative, bond-making

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24
Q

What is an endothermic reaction?

A

When a reaction absorbs energy, enthalpy change is positive, bond-breaking

25
Q

What is Standard enthalpy change?

A

The heat energy change measured under standard conditions (100 kPa and temperature of 298k)

26
Q

What is standard enthalpy of combustion?

A

The enthalpy change when 1 mole of a substance is burned completely in excess oxygen with all reactants and products in their standard states.

27
Q

What is standard enthalpy of formation?

A

The enthalpy change when 1 mole of a compound is formed from its elements under standard conditions (298K and 100kPa), all reactants and products being in their standard state.

28
Q

How to calculate heat change?

A

q= mc∆T

29
Q

What is Hess’s law?

A

The total enthalpy change in a chemical reaction is independent of the route by which the reaction takes place.

30
Q

What is mean bond enthalpy?

A

The enthalpy change needed to break the covalent bond into gaseous atoms, averaged over different molecules

31
Q

What is collision theory?

A

Reactions can only occur when collisions take place between particles having sufficient energy (activation energy)

32
Q

What is activation energy?

A

The minimum energy required in order for a successful collision to occur, for a reaction to happen

33
Q

Why do most collisions not lead to a reaction?

A

Colliding particles do not have sufficient kinetic energy or proper orientation in space

34
Q

What is rate of reaction?

A

The measure of the change in concentration of the reactants or the change in concentration of the products per unit time, moldm-3s-1

35
Q

What is a catlyst?

A

Substance that increases the rate of reaction without being changed in chemical composition or amount.

36
Q

How do catalysts work?

A

Provide an alternative reaction route of lower activation energy

37
Q

What is Le Chatelier’s principle?

A

The position of the equilibrium of a system changes to minimise the effect of any imposed change in conditions

38
Q

What is oxidation?

A

Electron loss, gain of oxygen, loss of hydrogen

39
Q

What is reduction?

A

Electron gain, loss of oxygen, gain hydrogen

40
Q

What is an oxidising agent?

A

Electron acceptors, they themselves are reduced

41
Q

What is a reducing agent?

A

Electron donors, they themselves are oxidised

42
Q

What is enthalpy of lattice dissociation?

A

The standard enthalpy change when 1 mole of an ionic crystal lattice form is separated into its constituent ions in gaseous form

43
Q

What is enthalpy of lattice formation?

A

The enthalpy change when 1 mole of solid ionic crystal lattice is formed from its separated gaseous ions (negative)

44
Q

What is enthalpy of formation?

A

The enthalpy change when 1 mole of a compound is formed from its constituent elements in their standard states

45
Q

What is ionisation energy?

A

The amount of energy required to remove one mole of electrons from one mole of gaseous atoms of an element to form one mole of gaseous ions

46
Q

What is enthalpy of atomisation?

A

The enthalpy change when one mole of gaseous atoms is formed from the element in its standard states, under standard conditions

47
Q

What is electron affinity?

A

The enthalpy changes when 1 mole of electrons is added to 1 mole of gaseous atoms/ions

48
Q

What is enthalpy of hydration?

A

Enthalpy change during the hydration (addition of water) of an ion in a solution

49
Q

How to calculate Gibbs free-energy change?

A

∆G = ∆H – T∆S

50
Q

What is entropy?

A

Measure of disorder in a thermodynamic system.

51
Q

What is a bronsted-lowry acid?

A

Proton donor

52
Q

What is a bronsted-lowry base?

A

Proton acceptor

53
Q

How to calculate pH?

A

pH = –log10[H+]

54
Q

How to calculate [H+]?

A

10^-pH

55
Q

How to calculate Kw?

A

Kw = [H+][OH–]

56
Q

How to calculate pKa?

A

pKa = –log10 Ka

57
Q

How to calculate Ka?

A

Ka= 10^-pka

58
Q

What is a buffer solution?

A

A solution that maintains an approximately constant pH upon the addition of small amounts of acid or base

Chemistry (2 decks)

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