Module 3- Periodic table and energy

Question 1

Periodicity

Answer 1

Repeating pattern across different periods

Question 2

Disproportionation

Answer 2

A reaction where an element simultaneously oxidises and reduces

Question 3

The activation energy

Answer 3

The minimum energy which particles need to collide to start a reaction

Question 4

Enthalpy change of reaction

Answer 4

When the number of moles of reactants as specified in the balanced equation react together

Question 5

Standard enthalpy change of formation of a compound

Answer 5

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

Question 6

Standard enthalpy of combustion of a substance

Answer 6

The enthalpy change that occurs when one mole of a substance is combusted completely in oxygen under standard conditions. (298K and 100kPa), all reactants and products being in their standard states

Question 7

Standard enthalpy change of neutralization

Answer 7

The enthalpy change when solutions of an acid and an alkali react together under standard conditions to produce 1 mole of water

Question 8

Mean bond enthalpy

Answer 8

The Enthalpy change when one mole of bonds of (gaseous covalent) bonds is broken (averaged over different molecules)

Question 9

Hess’s law

Answer 9

Total enthalpy change for a reaction is independent of the route by which the chemical change takes place

Question 10

initial rate

Answer 10

Rate at the start of the reaction where it is fastest

Question 11

Catalyst

Answer 11

increase reaction rates without getting used up

Question 12

Dynamic equilibrium

Answer 12

When forward and backward reactions are occurring at equal rates. The concentrations of reactants and products stays constant and the reaction is continuous

Question 13

Period

Answer 13

a horizontal trend in the periodic table. Elements show trends in properties across a period.

Question 14

Group

Answer 14

a vertical column in the periodic table. Elements in a group have similar chemical properties and their atoms have the same number of electrons in their outer-shell.`

Question 15

Periodicity

Answer 15

is the regular variation of elements with atomic umber and position in the periodic table.

Question 16

Thermal decomposition

Answer 16

breaking of chemical substance with heat into at least 2 chemical substances.

Question 17

Displacement reaction

Answer 17

is a reaction in which more reactive element displaces a less reactive element from an aqueous solution of the latters ions.

Question 18

Disproportionation

Answer 18

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

Question 19

Precipitation reaction

Answer 19

is the formation of a solid from a solution during a chemical reaction. Precipitates are often formed when 2 aqueous solutions are mixed together.

Question 20

Enthalpy, H

Answer 20

The heat energy stored in a chemical system

Question 21

Exothermic

Answer 21

When the enthalpy is smaller at then end of a reaction than at the beginning. Resulting in heat loss. Deltah -ve.

Question 22

Endothermic

Answer 22

When the enthalpy is greater at then end of a reaction than at the beginning. Resulting in heat being taken in. Deltah +ve

Question 23

Activation energy

Answer 23

Minimum energy required to start a reaction by the breaking of bonds.

Question 24

Enthalpy profile diagram

Answer 24

Shows the enthalpy of the reactants and products along with the activation energy and enthalpy change.

Question 25

Standard conditions

Answer 25

Pressure of 100kpa and Temperature of 298K. In solution concentration of 1M.

Question 26

Standard state

Answer 26

The state we find a substance in under standard conditions.

Question 27

Standard enthalpy change of reaction

Answer 27

Is the enthalpy change that accompanies the moles given in a balanced equation are reacted under standard conditions and in standard states

Question 28

Standard enthalpy change of combustion

Answer 28

Is the enthalpy change when one mol of reactant is burned completely in oxygen under standard conditions

Question 29

Standard enthalpy change of formation

Answer 29

Is the enthalpy change when 1 mol of product is formed from its constituent elements in standard states under standard conditions.

Question 30

Specific heat capacity, C

Answer 30

Energy required to heat 1g of substance by 1K.

Question 31

Bond enthalpy

Answer 31

Is the enthalpy change when 1 mol of given bonds is broken by homolytic fission in a gaseous state.

Question 32

Hess’ Law

Answer 32

“if a reaction can take place by more than 1 route and the initial and final conditions are the same, the total enthalpy change is the same for each route.”

Question 33

Rate of reaction

Answer 33

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

Question 34

Catalyst

Answer 34

A species than lowers the activation energy of a reaction by providing an alternate route but is not used itself.

Question 35

Boltzmann distribution

Answer 35

Is the distribution of energies of molecules within a sample at a given temperature.

Question 36

Dynamic equilibrium

Answer 36

An equilibrium in a closed system where the rate of forward reaction equals that of the reverse reaction leaving constant concentrations of products and reactants

Question 37

Le chatelier’s principle

Answer 37

When a change is imposed on a system in dynamic equilibrium the position of the equilibrium will change to minimise the change.