Enthalpy Changes 3.2.1

Question 1

What is the equation of Enthalpy Change?

Answer 1

Enthalpy Change = Enthalpy of Products - Enthalpy of Reactants
ΔH = prod - reac

Question 2

What is the Enthalpy Change of an Exothermic Reaction?

Answer 2

Negative

As energy is lost

Question 3

What is the Enthalpy Change of an Endothermic Reaction?

Answer 3

Positive

As energy is gained

Question 4

What is Activation Energy?

Answer 4

The energy needed to start a reaction

by breaking chemical bonds in the reactants

Question 5

What is the BOnd Dissasociation Energy?

Answer 5

The energy released when a particular bond is Homolytically (evenly) broken im the gaseous state

Question 6

Is breaking bonds Endo or Exothermic?

Answer 6

Endothermic as work is doen to break them

Question 7

Is forming bonds Endo or Exothermic?

Answer 7

Exothermic as energy is released

Question 8

What is a problem of Bond Enthalpy Calculations?

Answer 8

The substances are assumed to be gasseous at RTP

Mean bond enthalpies ae used

Question 9

What is the Specific Heat Formula?

Answer 9

Q = MCΔT
Q = Energy Change (joules)
M = Mass (grams)
C = Specific Heat Capacity (eg. water is 4.18)
ΔT = Temperature Difference (K)

Question 10

What is the Enthalpy Change of Combution?

Answer 10

The enthalpy change when one mole of a substance id completely combusted

Question 11

What is the Standard Enthalpy Change of Reaction?

Answer 11

The enthalpy change that accompanies a reaction in the molar quanities

Question 12

What is the Enthalpy Change of Formation?

Answer 12

When one mole of compoound is fromed from its constituent elements under standard conditions

Question 13

What is Hess’ Law?

Answer 13

Hess’ law states that if a reaction can take place by more than on route and the initial and final conditions are the same the total enthalpy chang eis the same