chapter 7: extent of chemical reactions

Question 1

what are irreversible reactions?

Answer 1

irreversible reactions can only proceed in one direction and cannot be reversed (reactants can only be converted into products, not products back to reactants)

Question 2

what are reversible reactions?

Answer 2

reversible reactions can proceed both forwards and backwards to a considerable extent

Question 3

what is an example of a reversible reaction?

Answer 3

the Haber-Bosch process, where ammonia is created from hydrogen and nitrogen gas

Question 4

what is meant by rate of reaction?

Answer 4

rate of reaction refers to how much product is formed over a given period of time.

Question 5

what can rate of reaction be influenced by?

Answer 5

temperature, concentration, pressure and catalysts

Question 6

what is the extent of reaction?

Answer 6

extent of reaction refers to proportion of reactants that have been converted into products.

Question 7

what is rate of reaction important to learning for?

Answer 7

for understanding the kinetics of a reaction and the factors that influence it.

Question 8

what is extent of reaction important to learning for?

Answer 8

extent of a reaction is important for understanding the yield of a reaction

Question 9

what is an open system?

Answer 9

in which matter and energy can be exchanged with the surroundings

Question 10

what is a closed system?

Answer 10

in which only energy is exchanged with the surroundings

Question 11

what does it mean by the yield of reaction?

Answer 11

amount of product obtained in a chemical reaction

Question 12

what is meant by a dynamic state of equilibrium?

Answer 12

in closed systems, dynamic equilibrium refers to when the forward and reverse reactions have not ceased, rather they occur simultaneously

Question 13

what are some things that happen during a dynamic equilibrium?

Answer 13

• as reactants and products are being produced at the same rate, there is no net change in the concentration of the products or reactants.
• the reaction is deemed incomplete, and all of the substances are present in the equilibrium mixture.
• temperature of the system is constant as heat is being absorbed at the same rate it is being released
• pressure of system is constant as number of gas particles is constant

Question 14

what does the equilibrium constant “K” represent?

Answer 14

it is the ratio of concentrations of products to the ratio of concentrations of reactants in a reaction.

Question 15

what do large K values represent?

Answer 15

reaction has progressed to considerable extent. there is a significant concentration of product in reaction system

Question 16

what do small K values represent?

Answer 16

reaction has not proceeded to a considerable extent and there is a considerable proportion of reactants present.

Question 17

how can we represent equilibrium reactions?

Answer 17

system reaching equilibrium can be represented by both concentration time graphs and rate time graphs.

Question 18

what is the only factor that affects K and why?

Answer 18

temperature. temperature changes alter the energy available to the system, when energy available to system is altered, reactants and products adjust to share that energy, which affects ratio of products to reactants in the system

Question 19

what happens when forward reaction is endothermic?

Answer 19

there is an increase in temperature, which leads to an increase in the extent of the reaction, and hence an increase in the value of K

Question 20

what happens when forward reaction is exothermic?

Answer 20

increase in temperature leads to decrease in the extent of reaction, and a decrease in the value of K

Question 21

what is Q?

Answer 21

Q is a reaction quotient that serves as a quantitative measure of the extent of a reaction.

Question 22

what happens when Q<K

Answer 22

forward reaction is favoured and system shifts to the right

Question 23

what happens when Q = K?

Answer 23

Equilibrium

Question 24

what happens when Q > K

Answer 24

Reverse reaction is favoured (shifts left)

Question 25

what is the reverse of K?

Answer 25

1/K forwards