C6: The rate and extent of chemical reactions

Question 1

How is rate of reaction calculated?

Answer 1

Rate = amount of product formed or reactant used ‘/. Time

Question 2

Name three ways of measuring rate of reaction

Answer 2

1) loss in mass of reactant
2) volume of gas produced
3) time for solution to become opaque

Question 3

Describe measuring the rate by monitoring the disappearance of a cross.

Answer 3

Take a piece of paper and mark a cross (X) on it. Put the reaction flask on this cross. Mix the reagents, and measure how long it takes for a cloudy mixture to conceal the cross.

Question 4

Factors affecting rate of reaction and how?

Answer 4

INCREASE CONC/PRESSURE:
-more particles in a volume,increases frequency of collisions…more successful collisions, so rate increases

TEMPERATURE:
-particles gain KE , collide more frequently,rate increase

SURFACE AREA:
- More SA:V, increases frequency of successful collisions, increasing rate

CATALYST:
- provide alternative reaction pathway to products with lower activation energy
- frequ of successful collison increases

Question 5

what is meant by dynamic equilibrium?

Answer 5

-occurs in a CLOSED SYSTEM

-molecules on right/left of equation will chaNge into eachother SIMULTANEOUSLY, at the SAME RATE

-conc of products/reactants will stay the SAME

Question 6

When is dynamic equilibrium reached?

Answer 6

In a closed system , when the forward and reverse reactions occur at the same rate and the concentrations of reactants and products remain constant.

Question 7

What is the Le Chatelier’s Principle?

Answer 7

If conditions of a system at equilibrium change , the position of equilibrium move to oppose the change

Question 8

Describe the effect of changing concentration of reactant and product on the position of the equilibrium

Answer 8

If concentration is changed, the system is NO LONGER at equilibrium and will move until equilibrium is reached again.
If concentration of a product is increased, the position of equilibrium will move (away from product)so that more reactants are formed
If concentration of a reactant is increased, the position of equilibrium will move (away from reactants) so that more products are formed.

If conc of a product is decreased, more reactants will react until equilibrium is reached.

Question 9

Describe the effect of changing temperature on the position of equilibrium

Answer 9

If the temp is increased, the position of equilibrium shifts towards the endothermic side increases and yield increases(for endothermic side)
If the temp is decreased, equilibrium shifts towards the exothermic side increases and yield increases (for exothermic side)

Question 10

Describe the effect of changing pressure on the position of equilibrium

Answer 10

If pressure is increased, the equilibrium position will shift towards the side with the smaller number of molecules
If pressure is decreased, the equilibrium position will shift towards the side with the larger number of molecules.

Question 11

Describe the effect of a catalyst on the position of equilibrium

Answer 11

There is no effect.
A catalyst will just speed up the forward and backward reactions so equilibrium is reached faster.