energy change and rate of reaction

Question 1

heat of reaction

Answer 1

• the net change of chemical potential energy of the system

Question 2

exothermic reactions

Answer 2

• reactions which transform chemical potential energy into thermal energy

Question 3

endothermic reactions

Answer 3

• reactions which transform thermal energy into chemical potential energy

Question 4

bond breaking vs. bond forming

Answer 4

• endothermic

- exothermic

Question 5

activation energy

Answer 5

• minimum energy required to start a chemical reaction

- the energy required to form the activated complex

Question 6

activated complex

Answer 6

• a high energy, unstable, temporary transition state between the reactants and the products

Question 7

reaction rate

Answer 7

• the change in concentration per unit time of either a reactant or product

Question 8

way to measure reaction rate

Answer 8

• change in volume of a gas produced
• change in mass
• turbidity (precipitate formation)
• change in colour

Question 9

catalyst

Answer 9

• a substance that increases the rate of the reaction but remains unchanged at the end of the reaction

Question 10

collision theory

Answer 10

• correct orientation
• sufficient energy (kinetic energy greater or equal to activation energy)
• reaction rate is directly proportional to the number of effective collisions per unit time

Question 11

average rate of reaction

Answer 11

= (amount of AB^2) / (time taken)

Question 12

affecting rate of reaction

Answer 12

• surface area (solid)
• concentration (solution)
• pressure (gas)
• temperature
• catalyst

Question 13

explanation

Answer 13

• more contact points between particles ; greater frequency of collective collisions ; increase in rate of reaction
• increase in number of particles per unit volume ; greater frequency of effective collisions ; increase in the rate of reaction
• decrease in volume = more particles per unit volume ; greater frequency of effective collisions; increase rate of reaction
• greater kinetic energy (more particles have greater energy than activation energy) ; greater frequency of effective collisions ; increase rate of reaction
• reduces activation energy ; more particles with Ek > Ea ; greater frequency of effective collisions ; increase in rate of reaction