Topic 5 Chemical Energetics

Question 1

Enthalpy change of reaction

Answer 1

The enthalpy change when the reactants in the stoichiometric equation react to give the products under standard conditions

Question 2

Enthalpy change of formation

Answer 2

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

Question 3

Enthalpy change of combustion

Answer 3

The enthalpy change when one mole of a substance is burnt in excess oxygen under standard conditions

Question 4

Enthalpy change of neutralisation

Answer 4

The enthalpy change when one mole of water is formed by reacting an acid with an alkali under standard conditions

Question 5

Standard pressure and temperatures are?

Answer 5

101kPa, 298k

Question 6

transition stage is?

Answer 6

state during a reaction at which chemical bonds are partially broken and formed

Question 7

Exothermic reactions

Answer 7

-reactants are higher in energy than products
-reactants are closer to transition stage
-so exothermic reactions have a lower Ea

Question 8

Endothermic

Answer 8

-reactants are lower in energy than products
-products are closer to transition stage
-so endothermic reactions have higher Ea

Question 9

Bond dissociation energy

Answer 9

The amount of energy required to break one mole of a specific covalent bond in the gas phase

Question 10

Specific heat capacity of water is?

Answer 10

4.18Jg^-1C^-1

Question 11

q=mcΔT

Answer 11

q= The heat transferred (J)
m= mass of water (g)
c=specific heat cap. of water(4.18)
ΔT= change of temp.