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Chemistry > Definitions > Flashcards

Definitions Flashcards

1
Q

Acid

A

A species that is a proton (H+) donor

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2
Q

Activation Energy

A

The minimum energy required to start a reaction by the breaking of bonds

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3
Q

Adsorption

A

The process that occurs when a gas, liquid or solute is held to the surface of a solid (IN THE CATALYTIC CONVERTER

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4
Q

Alkali

A

A type of base that dissolves in water forming hydroxide ions, OH-(aq)

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5
Q

Anhydrous

A

A substance containing no water molecules

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6
Q

Anion

A

A negatively charged ion

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7
Q

Atom economy

A

Mr of desired product
————————————— x100
Sum of Mr of all products

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8
Q

Atomic orbital

A

A region within an atom that can hold up to two electrons with opposite spins

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9
Q

(Average) bond enthalpy

A

The (average) enthalpy change that takes place when breaking by homolytic fission 1 mol of a given type of bond in the molecules of a gaseous species

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10
Q

Avogadro constant

A

The number of atoms per mol of the carbon-12 isotope (6.02 x 10^23)

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11
Q

Base

A

A species that is a proton (H+) acceptor

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12
Q

Catalyst

A

A substance that increases the rate of a chemical reaction without being used up in the process

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13
Q

Cation

A

A positively charged ion

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14
Q

Cis-trans isomerism

A

A special type of E/Z isomerism in which there is a non-hydrogen group and hydrogen on each Carbon of a C=C double bond. The cis isomer (Z) has the hydrogen atoms on each carbon on the same side; the trans isomer (E) has the hydrogen atoms on each carbon on different sides.

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15
Q

Coordinate / Dative covalent bond

A

A shared pair of electrons provided by one of the bonding atoms only

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16
Q

Covalent bond

A

A bond formed by a shared pair of electrons

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17
Q

Disproportionation

A

The oxidation and reduction of the same element in a redox reaction

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18
Q

Dynamic equilibrium

A

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

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19
Q

E/Z isomerism

A

A type of stereoisomerism in which different groups attached to each carbon 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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20
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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21
Q

Electrophile

A

An atom (or group of atoms) that is attracted to an electron rich centre (double bonds), where it accepts a pair of electrons to form a new covalent bond

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22
Q

Empirical formula

A

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

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23
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 (delta H is positive)

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24
Q

Enthalpy

A

The heat that is stored in a chemical system

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25
Q

Standard enthalpy change of combustion

A

The enthalpy change that takes place when one mole of a substance burns completely in oxygen under standard conditions, with all reactants and products being in their standard states

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26
Q

Standard enthalpy change of formation

A

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

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27
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, with all reactants and products being in their standard states

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28
Q

Exothermic reaction

A

A reaction in which the enthalpy of the products is less than the enthalpy of the reactants, resulting in heat loss to the surroundings (delta H is negative)

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29
Q

Fractional distillation

A

The separation of the components in a liquid mixture into fractions which differ in boiling point by means of distillation, using a fractionating column

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30
Q

Fragmentation

A

The process in mass spectrometry that causes a positive ion to split into pieces, one of which is a positive fragment ion

31
Q

Functional group

A

The part of the organic molecule responsible for its chemical reactions

32
Q

General formula

A

The simplest algebraic formula of a member of a homologous series (CnH2n+2 for alkanes)

33
Q

Greenhouse effect

A

The process in which the absorption and subsequent emission of infrared radiation by atmospheric gases warms the lower atmosphere and the planet’s surface

34
Q

Hess’ law

A

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

35
Q

Heterogenous catalysts

A

Where the catalyst has a different physical state from the reactants- often reactants are gases and the catalyst is solid (CATALYTIC CONVERTER)

36
Q

Heterolytic fission

A

The breaking of a covalent bond with both of the bonded electrons going to one of the atoms forming a cation (+) and an anion (-)

37
Q

Homologous series

A

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

38
Q

Homolytic fission

A

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

39
Q

Hydrated

A

Crystalline and containing water molecules

40
Q

Hydrogen bond

A

A strong dipole-dipole attraction between an electron deficient hydrogen atom on one molecule and a lone pair of electrons on a highly electronegative atom (O, N or F)

41
Q

Ionic bond

A

The electrostatic attraction between oppositely charged ions

42
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

43
Q

le Chatelier’s principle

A

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

44
Q

Metallic bond

A

The electrostatic attraction between positive metal ions and delocalised electrons

45
Q

Mole

A

The amount of any substance containing as many particles as there are carbon atoms in exactly 12g of the carbon-12 isotope

46
Q

Molecular ion, M+

A

The positive ion formed in mass spectrometry when a molecule loses an electron

47
Q

Nucleophile

A

An atom or group of atoms that is attracted to an electron deficient centre where it donates a pair of electrons to form a new covalent bond

48
Q

Percentage yield

A

actual amount in mol of product
——————————————————– x100
theoretical amount in mol of product

49
Q

Periodicity

A

A regular periodic variation of properties of elements with atomic number and position in the Periodic table

50
Q

Permanent dipole

A

A small charge difference across a bond resulting from a difference in electronegativities of the bonded atoms

51
Q

Permanent dipole-dipole force

A

An attractive force between permanent dipoles in neighbouring polar molecules

52
Q

Pi bond

A

The reactive part of a double bond formed above and below the plane of the bonded atoms by sideways overlap of p-orbitals

53
Q

Polar covalent bond

A

A bond with a permanent dipole

54
Q

Polar molecule

A

A molecule with an overall dipole, taking into account any dipoles across bonds

55
Q

Radical

A

A species with an unpaired electron

56
Q

Rate of reaction

A

The change in concentration of a reactant or a product in a given time

57
Q

Redox reaction

A

A reaction in which both oxidation and reduction take place

58
Q

Reflux

A

The continual boiling and condensing of a reaction mixture to ensure that the reaction takes place without the contents of the flask boiling dry

59
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

60
Q

Relative isotopic mass

A

The mass of an atom of an isotope compared with one twelfth of the mass of an atom of carbon-12

61
Q

Salt

A

A chemical compound formed from an acid, when a H+ ion from the acid has been replaced by a metal ion or another positive ion, such as the ammonium ion NH4+

62
Q

Saturated hydrocarbon

A

Single bonds only

63
Q

Shell / main energy level

A

A group of atomic orbitals with the same principal quantum number, n

64
Q

Specific heat capacity, c

A

The energy required to raise the temperature of 1g of a substance by 1°C

65
Q

Spectator ions

A

Ions that are present but take no part in a chemical reaction

66
Q

Standard conditons

A

Pressure of 100kPa (1 atm), Temperature of 25°C (298K) and a concentration of 1 mol dm-3

67
Q

Stereoisomers

A

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

68
Q

Structural isomers

A

Molecules with the same molecular formula but with a different structural arrangement of atoms

69
Q

Sub-shell

A

A group of the same type of atomic orbitals (s, p, d or f) within a shell

70
Q

Unsaturated hydrocarbon

A

Contains carbon-carbon multiple bonds

71
Q

van der Waals’ forces

A

Very weak attractive forces between induced dipoles in neighbouring molecules

72
Q

Volatility

A

The ease with which a liquid turns into a gas. This increases as boiling point decreases

73
Q

Water of crystallisation

A

Water molecules which form an essential part of the crystalline structure of a compound

Chemistry (2 decks)

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