Rates Of Reaction

Question 1

What is the enthalpy change for a reaction?

Answer 1

Measure of heat energy added to a system
With constant pressure (100KPa) and temperature (293K)
Using the molar amounts

Question 2

Describe what happens in an endothermic reaction

Answer 2

The energy required to break the bonds is greater than the energy released when bonds are formed

Question 3

Describe what happens in an exothermic reaction

Answer 3

The energy released when bondas are formed is greater than energy required to break the bonds

Question 4

Define bond enthalpies

Answer 4

Amount of heat energy required to break one mole of a covalent bond in the gaseous state to form separate gaseous atoms

Question 5

Collision theory states that

Answer 5

In order for a reaction to occur:
Particles must collide
With enough energy
In the correct orientation

Question 6

What effect does increasing surface area have on rate of reaction?

Answer 6

Greater area for collisions to occur
Increased frequency of successful collisions
Faster rate

Question 7

What effect does increasing concentration of solutions have on rate of reaction?

Answer 7

More particles per unit volume
Increase in frequency of successful collisions

Question 8

What effect does increasing pressure of gases have on rate of reaction?

Answer 8

More particles per unit volume
Increase in frequency of successful collisions

Question 9

How does increasing temperature of reaction mixture increase rate of reaction?

Answer 9

Particles move faster and have more energy
Increase in frequency of collisions
Therefore increase in frequency of successful collisions

Question 10

How does a catalyst increase rate of reaction?

Answer 10

Provides an alternative pathway for the reaction mixture
With a lower activation energy
More collisions with required activation energy
Therefore increased frequency of successful collisions

Question 11

Standard enthalpy change of formation

Answer 11

Enthalpy change when one mole of a compound is formed from its elements
Under standard conditions
All products and reactants in standard states

Question 12

Standard enthalpy change of combustion

Answer 12

Enthalpy change when one mole of substance combusts with sufficient oxygen
Under standard conditions
All products and reactants in standard states

Question 13

Standard enthalpy change of neutralisation

Answer 13

Enthalpy change when one mole of H+ ions react with one mole of OH- ions to form one mole of H2O
Under standard conditions
With all products and reactants in standard states