Module 3 NTK definitions

Question 1

What is periodicity?

Answer 1

The repeating trends in physical and chemical properties:
Elements are arranged by increasing atomic (proton) number - in groups with similar chemical properties

Question 2

What are s/p/d elements?

Answer 2

A s/p/d element has its highest energy electron in a s/p/d subshell

Question 3

What is first ionisation energy?

Answer 3

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

Question 4

What is metallic bonding?

Answer 4

Strong electrostatic attraction between positively charged ions (cations) and delocalised electrons

Question 5

What is disproportionation?

Answer 5

The simultaneous oxidation and reduction of the same element (in the same redox reaction)

Question 6

What is an exothermic reaction?

Answer 6

A reaction where heat energy is released to the surroundings (enthalpy change is negative)

Question 7

What is an endothermic reaction?

Answer 7

A reaction where heat energy is absorbed from the surroundings (enthalpy change is positive)

Question 8

What is average bond enthalpy?

Answer 8

The average enthalpy change for the breaking of one mole of bonds in gaseous molecules (by homolytic fission)

Question 9

What are the standard conditions?

Answer 9

• Temperature is 25°C (298K)
• Pressure 1 atm (100kPa)
• All solutions have the concentration of 1.00 mol/dm^3

Question 10

What is standard enthalpy change of neutralisation?

Answer 10

The enthalpy change that accompanies the formation of one mole of H2O(l) from neutralisation in their standard states under standard conditions

Question 11

What is standard enthalpy change of formation?

Answer 11

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

Question 12

What is standard enthalpy change of combustion?

Answer 12

The enthalpy change for complete combustion of one mole of a substance under standard conditions, all reactants and products being in their standard states

Question 13

What is rate of reaction?

Answer 13

The change in concentration of a reactant or a product per unit time
Rate = concentration of reactant/product mol/dm^3 / Time s

Question 14

What is activation energy?

Answer 14

The minimum energy required to start a reaction by breaking bonds

Question 15

What is a heterogeneous catalyst?

Answer 15

Catalysis of a reaction in which the catalyst has a different physical state from the reactants

Question 16

What is a homogeneous catalyst?

Answer 16

Catalysis of a reaction in which the catalyst and the reactants are in the same physical state

Question 17

What is dynamic equilibrium?

Answer 17

Exists in a closed system, when the rate of the forward reaction is equal to the rate of the reverse reaction, and the concentrations of reactants and products do not change

Question 18

What is Le Chateilier’s principle?

Answer 18

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