Chem definitions

Question 1

What is a alkane

Answer 1

Saturated hydrocarbon with the general formula CnH2n+2

Question 2

Define free radical

Answer 2

Uncharged species with an unpaired electron that is used to form a covalent bond

Question 3

Substitution reaction

Answer 3

Reaction in which one atom or group is replaced by another atom or group. Always two reactants and two products

Question 4

What is a pi bond

Answer 4

Two p-orbitals overlapping above and below the internuclear axis

Question 5

What is a biofuel

Answer 5

A biofuel is made from renewable organic materials, such as sugar, grain, or vegetable oils

Question 6

Define the term electronegativity

Answer 6

Electronegativity of an element is the ability which it attracts a pair of electrons in a covalent bond towards itself

Question 7

Standard enthalpy of formation

Answer 7

The enthalpy change when mol if a substance is formed from it’s elements in their standard states at 1 atm less here and at a stated temperature, usually 298K

Question 8

Standard enthalpy of reaction

Answer 8

The enthalpy change when the number of moles of the substances in the equation as written react under standard conditions of 1 atm pressure and a stated, usually 298K

Question 9

Standard enthalpy of formation

Answer 9

The enthalpy change when 1 mol of a substance is formed from it’s elements in their standard states at 1 atm pressure and at a stated temperature, usually 298K

Question 10

Standard enthalpy of combustion

Answer 10

The enthalpy change when 1 mol of the substance is burnt in excess oxygen and under standard conditions of 1 atm pressure and a stated temperature (25*C)

Question 11

Specific heat capacity

Answer 11

Heat requires to increase the temperature of 1g of the substance by 1*C

Question 12

Ectothermic reaction

Answer 12

Chemical energy is converted into heat energy and the temperature rises

Question 13

Endothermic reaction

Answer 13

Heat energy is converted into chemical energy and the temperature system falls

Question 14

Enthalpy

Answer 14

The chemical energy in the system at constant pressure that can rn converted into heat

Question 15

Define the term enthalpy change of reaction

Answer 15

Enthalpy change when the number of moles of reactants, react as specified in the balanced equation

Question 16

Addition reaction

Answer 16

Two reactants form a single product

Question 17

Substitution reaction

Answer 17

One atom or group of atoms replaces another atom or group of atoms in a molecule

Question 18

Elimination reaction

Answer 18

Two atoms are removed from adjacent carbon atoms in a molecule of an organic substance

Question 19

Polymerisation

Answer 19

Thousands of monomer molecules join together to form a long polymeric chain

Question 20

Oxidation

Answer 20

Addition of oxygen or removal of hydrogen

Question 21

Hydrolysis

Answer 21

Water splits an organic molecule into two parts

Question 22

Nucleophile

Answer 22

A species with a lone pair of electrons that it uses to form a covalent bond

Question 23

Electrophile

Answer 23

Attacks places of high electron density and forms a covalent with a pair of electrons from the electron rich site

Question 24

Molecular formula

Answer 24

Shows the number of atoms of each element in one molecule of the substance

Question 25

Empirical formula

Answer 25

The simplest whole number ratio of the atoms of each element in the substance

Question 26

Structural formula

Answer 26

Unambiguous structure that shows how the atoms in the molecule are arranged