C6.3 pt 1

Question 1

What is a reversible reaction

Answer 1

It is a reaction that can go in both directions. The products can react together to make the original reactants. If a reversible reaction is exothermic in one direction, it is endothermic in the other direction. A equilibrium, the rate of the forward reaction is the same as the rate of the reverse reaction.

Question 2

Equilibrium

Answer 2

In order for equilibrium of a reversible reaction to happen, the reactants must be in a closed system/ sealed container. A chemical reaction in a closed system is in dynamic equilibrium when the forwards and backwards reaction occur at the same rate. At chemical equilibrium the concentration of the reactants and products remain constant.

Question 3

Key point

Answer 3

The exothermic reaction heats up a reaction whereas an endothermic reaction cools down a reaction

Question 4

Le Chatelier’s principle

Answer 4

If a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract the change

Question 5

Temperature

Answer 5

If a reaction is exothermic and the temperature decreases the shift in equilibrium will happen in the exothermic direction and the yield increases and ROR will decrease

If a reaction is endothermic and the temperature increases, the shift in equilibrium will happen in the endothermic direction as the yield and ROR increases

If a reaction is endothermic and the temp decrease, the shift in equilibrium will happen in the exothermic direction as yield and ROR decreases

Question 6

Issue with changing temperature of exothermic reversible reactions

Answer 6

If the temperature of an exothermic reaction is decreased, yield may increase but ROR decreases- this can be solved by using a compromised temperature

Question 7

What is a catalyst

Answer 7

A substance that speeds up the rate of reaction without being used up in the reaction by providing an alternative pathway with a lower activation energy

Question 8

Key points for pressure

Answer 8

Only for gaseous systems
Depends on how many moles of gas on each side
The effect on product yield always depends on if products side has fewer moles

Question 9

Pressure

Answer 9

If pressure in a reaction increases, the shift in pressure will go to the side with fewer moles of gas to relieve pressure and ROR is increased

If pressure decreases, the shift in pressure will go to the side with more moles of gas to increase pressure and ROR is decreased

Question 10

Concentration

Answer 10

If concentration in a reaction increases, the shift in concentration will be to the side with less mol/dm3 and the product yield/ROR will increase

If concentration decreases, the shift in concentration will be to the side with more mol/dm3 and the product yield/ROR will decrease