Chemistry definition

Question 1

Isotope

Answer 1

atoms of the same element with the same number of protons but different numbers of neutrons

Question 2

Relative atomic mass

Answer 2

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

Question 3

Relative isotopic mass

Answer 3

average mass of an isotope relative to 1/12th of mass of carbon-12 atom

Question 4

Orbital

Answer 4

region around the nucleus that can hold up to 2 electrons with opposite spins

Question 5

1st Ionisation Energy

Answer 5

energy change when one molecule of electrons is removed from one mole of gaseous atoms

Question 6

Acid

Answer 6

proton donor

Question 7

Base

Answer 7

proton acceptor

Question 8

Salt

Answer 8

made when proton of an acid is replaced by a metal ion or NH4

Question 9

Oxidation

Answer 9

loss of electrons or increase in oxidation number

Question 10

Reduction

Answer 10

gain of electrons or decrease in oxidation number

Question 11

Disproportionation

Answer 11

reaction where an element is simultaneously oxidised and reduced

Question 12

Amount of substance

Answer 12

the number of moles of substance

Question 13

Mole

Answer 13

amount of substances containing 6.02*10^23 particles

Question 14

Avogadro constant, Na

Answer 14

number of particles present in a mole(6.02*10^23)

Question 15

Ionic bond

Answer 15

strong electrostatic attraction between positive ions and negative ions

Question 16

Covalent bond

Answer 16

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

Question 17

Dative covalent bond(Coordinate bond)

Answer 17

shared pair of electrons with one atom contributing both electrons

Question 18

Metallic bond

Answer 18

electrostatic attraction between positive ions and delocalised electrons

Question 19

Electronegativity

Answer 19

power of an atom to attract the bonding electron in a covalent bond

Question 20

Periodicity

Answer 20

repeated patterns across periods of the periodic table

Question 21

Enthalpy of reaction

Answer 21

enthalpy change when one mole of reactants in a specified chemical equation

Question 22

Standard enthalpy of formation

Answer 22

enthalpy change when one mole of compound forms from its element in their standard states under standard condition

Question 23

Standard enthalpy of combustion

Answer 23

enthalpy change when one mole of compound undergoes complete combustion in oxygen under standard condition

Question 24

Standard enthalpy change of neutralisation

Answer 24

enthalpy change when one mole of water forms when an aqueous acid neutralises aqueous base under standard condition

Question 25

Standard conditions

Answer 25

100Kpa and 293K

Question 26

Bond enthalpy

Answer 26

the energy needed to break 1 mole of covalent bonds in a substance in the gaseous state

Question 27

Activation energy, Ea

Answer 27

minimum energy a particle must have for a reaction to occur

Question 28

Homogeneous catalyst

Answer 28

catalyst in the same state as the reactants

Question 29

Heterogenous catalyst

Answer 29

catalyst in a different state from the reactants

Question 30

Dynamic equilibrium

Answer 30

rate of forward and reverse reaction are equal. concentration of reactants and products are constants.

Question 31

Rate of reaction

Answer 31

rate of change of concentration of reactants or products

Question 32

Order of reaction

Answer 32

power of reactant’s concentration in the rate equation

Question 33

rate constant

Answer 33

the constant proportionality, k, in the rate equation

Question 34

half-life

Answer 34

the time for the concentration of a reactant to fall to half its original value

Question 35

rate-determining step

Answer 35

the slowest step