Definitions

Question 1

Ionic Bonding

Answer 1

Electrostatic attraction between positively and negatively charged ion.

Question 2

Covalent Bonding

Answer 2

Electrostatic attraction between shared pair of electrons and bonding nuclei.

Question 3

Metallic Bonding

Answer 3

Electrostatic attraction between positive metal ions and sea of delocalised electrons

Question 4

Electronegativity

Answer 4

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

Question 5

Enthalpy

Answer 5

H

A measure of the heat energy in a chemical system (atoms, molecules or ions)

Question 6

Enthalpy Change

Answer 6

^H = H(products) - H(reactants)

Question 7

Activation Energy

Answer 7

The minimum energy required for a reaction to take place.

Question 8

Average Bond Enthalpy

Answer 8

The energy required to break one mole of a specific type of bond in a gaseous molecule.

Question 9

Ionisation Energy

Answer 9

The energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous +1 ions.

Question 10

Second Ionisation Energy

Answer 10

Energy required to remove one electron from each atom in one mole of gaseous +1 ions of an element to form one mole of gaseous +2 ions.

Question 11

Homogeneous Catalyst

Hetrogeneous Catalyst

Answer 11

The same physical state as reactants

Other physical states as reactants

Question 12

Brownsted Lowry Acid

Answer 12

Proton donor

Question 13

Browbstead Lowry Bad

Answer 13

Proton Acceptor

Question 14

Buffer Solution

Answer 14

a system that minimises pH changes when small amounts of an acid or base are added. They contain a weak acid and its conjugate base.

Question 15

Lattice Enthalpy

Answer 15

The enthalpy change that accompanies the formation of one mole of a ionic compound. Forms gaseous ions under standard conditions.

Question 16

Enthalpy change of Neutralisation?

Answer 16

The energy change that accompanies the reaction of and acid by a base to form one mole of H20 (l), under standard conditions.

Question 17

Enthalpy change of Combustion?

Answer 17

The enthalpy change that take place when one mole of a substance reacts completely with oxygen, under standard conditions.

Question 18

Enthalpy change of Formation?

Answer 18

Enthalpy change that takes place when one mole of a compound is formed from its elements, under standard conditions.

Question 19

Intermolecular forces:
Permanent dipole- induced dipole

Permanent dipole- permanent dipole

Instantaneous- induces dipole

Hydrogen bonding

Answer 19

Molecule with permanent dipole induce dipole on non molar molecule

Attraction between two polar molecules

Random electron movement creates instantaneous dipole, that induces the neighbouring molecule

Requires a lone pair of electrons as electronegative attraction is created to exposed H nucleus

Question 20

Halogen Group?

Answer 20

At room temp and pressure, exist as diatomic molecules. Group changes from gas to liquid to solid down the group.

Reactivity decreases down the group. As there is less attraction

Question 21

Qualities Analysis?

Answer 21

1) Carbonate test - add dilute HNO3, bubbles, can then bubble through lime water
2) sulphate test - add BaNO3 form BaSO4 (s)
3) Halide test - add AgNO3
Chloride = white ppt, soluble in dilute NH3
Bromine = cream ppt, soluble in conc. NH3
Iodine = yellow ppt, insoluble in conc. NH3

Question 22

Le Chateliers Principle

Answer 22

Conc - if more products are formed, equilibrium shifts to the right
Temp - if endothermic, equilibrium to the right, take in heat energy, minimise increase in temp
Pressure - only for gas, depends on no. Of molecules on each side, e.g. if more molecules on LHS, increase pressure will mean shift to the right with fewer molecules

Question 23

Kc?

Answer 23

Kc = [C]c[D]d / [A]a[B]b

Kc = 1 equilibrium halfway
Kc > 1 equilibrium towards products
Kc < 1 equilibrium towards reactants

Question 24

Arrhenius Equation?

Answer 24

K = Ae^-Ea/RT

Log form - LnK = -Ea/RT + LnA

Question 25

Partial pressure and mole fraction?

Answer 25

Mole fraction = number of moles of A / total number of moles in a gas mixture

Partial pressure = mole fraction of A X total pressure

Question 26

Kp?

Answer 26

Kp = p[HI]^2 / p[H2] x p[I2]

Exothermic reaction - K will decrease with increasing pressure, raising temp would decrease yield.
This is because the ratio of p[HI]^2 / p[H2] x p[I2] will be greater than Kp, for this to be proportional equilibrium shift to left so [HI]^2 hast to decrease and H2 and I2 has to increase, create equal ratio.

Endothermic - Kp increase with increasing temp, equilibrium shift to the right, increasing yield

Question 27

pH and H+?

Pka and Ka?

Answer 27

pH = -log(H+)

(H+) = 10^-pH

Pka = -log(Ka)

(Ka) = 10^-Pa

Question 28

Kw?

Answer 28

Ionic product of water

Kw = [H+][OH]

Kw = 1x10^-14

Question 29

Entropy?

Answer 29

The greater the entropy, the greater the dispersal of energy and the greater the disorder.

• at 0K no energy to disperse, entropy will be 0
• above 0K energy disperses, substances have positive entropy

• Standard Entropy always POSITIVE

Question 30

Calculating entropy change?

Answer 30

🔼S* = ES* (products) - ES* (reactants)

Question 31

Gibbs Free energy?

Answer 31

🔼G, overall change in energy during chemical reactions

🔼G = 🔼H - T🔼S

T = 🔼H/🔼S

🔼G < 0 in order to be feasible