Chemical equilibrium notes questions

Question 1

What are features of chemical equilibirium?

Answer 1

1. the rate of the forward and reverse reactions are equal

2. the concentrations of the reactants and products remain constant

Question 2

What can you change so the eqbm change?

Answer 2

1. temperature
2. total pressure
3. concentration

Question 3

What is le Chatelier’s principle?

Answer 3

A system at eqbm will oppose any change opposed upon it by shifting the eqbm

Question 4

What will happen to the eqbm if the concentration of a reactant increases?

Answer 4

the eqbm shifts right to oppose the increase in [reactants] and reduce the constraint

Question 5

What will happen to the eqbm if the concentration of a reactant decreases?

Answer 5

the eqbm shifts left to oppose the decrease in [reactants] and reduce the constraint

Question 6

What will happen if the total pressure of an eqbm is increased?

Answer 6

the eqbm shifts to the side with fewer moles of gas

Question 7

There are fewer moles on the products side. What will happen to the yield and eqbm position if the total pressure is increased?

Answer 7

1. eqbm shifts right
2. so the product yield increases
3. as there are fewer moles of gas on the right hand side so the eqbm shifts right to oppose the increase in pressure

Question 8

reacting side: 3 moles……. products side: 3 moles . What will happen to the yield and eqbm position if the total pressure is increased?

Answer 8

1. no change to eqbm position
2. so no change in product yield
3. as equal moles on either side

Question 9

There are fewer moles on the reacting side. What will happen to the yield and eqbm position if the total pressure is increased?

Answer 9

1. eqbm shifts left
2. so product yield decreases
3. as there are fewer moles of gas so eqbm shifts left to oppose the increase in pressure

Question 10

According to Le Chatelier’s principle what will happen to the eqbm position if the temperature is increased?

Answer 10

An increase in temperature shifts the eqbm in the endothermic direction

Question 11

How do you know if a reaction is exothermic?

Answer 11

AH (enthalpy change) is a negative number

Question 12

If a (forward - they always mean forward) reversible reaction is exothermic what will happen to the eqbm position if the temperature is increased?

Answer 12

1. eqbm shifts left
2. product yeild decreases
3. because the eqbm shifts in the endothermic direction to oppose the increase in temperature
4. by absorbing heat energy

Question 13

If a (forward -they always mean forward) reversible reaction is endothermic what will happen to the eqbm position if the temperature is increased?

Answer 13

1. eqbm shifts right
2. so product yield increases.
3. The eqbm shifts right in the endothermic direction to opppose the increase increase in temperature
4. by absorbing excess heat energy

Question 14

What effect does the addition of a catalyst have on the rate of a reversible reaction?

Answer 14

once at eqbm, a catalyst speeds up the rate of forward and reverse reactions EQUALLY

Question 15

Why might a catalyst be used in a reversible reaction?

Answer 15

initially catalysts are very effective because they speed up he rate of ATTAINMENT of equilibrium

Question 16

What effect does the addition of a catalyst have on a mixture at equilibrium?

Answer 16

no effect on the yield

Question 17

If a reaction is created in conditions of low temperature, that produces high yield, what can be said about the type of reaction it is? And why?

Answer 17

reaction is exothermic because low temperature produces a high product yield

Question 18

In industry why would the operating temperature and pressure be 400 degrees and 5MPa be used in an exothermic reaction?

Answer 18

1. A moderate temperature is used as otherwise the raate of reaction would be slow.
2. The pressure is reasonably high but an even higher pressure is NOT USED
3. because of the high cost and energy demand of electrical pumping