unit 11 - rate of reaction and equilibrium

Question 1

collision theory

Answer 1

for a sucessfull reaction, particles must collide with sufficient energy in the corrent orientation

Question 2

activation energy

Answer 2

Min. amount of energy required by reacting materials to break down existing bonds and form new ones

Question 3

to increase rate of reaction 2 simplest things to do?

Answer 3

more frequent collision
more successful collisions

Question 4

how to measure activation enegry?

Answer 4

difference between the activation complex and reactants energy

Question 5

how to achieve more frequenct collisions?

Answer 5

increase particle speed or increase particles present

Question 6

how to acheieve more successful collisions?

Answer 6

give particle more energy or lower activation energy

Question 7

how to calculate rate of reaction

Answer 7

Amount of reactant used/time
or
Amount of product formed/time

Question 8

A steeper curve in the reaction graph indicates

Answer 8

a faster rate of reaction

Question 9

whose concentration increases and decreases in a reaction?

Answer 9

concentration of reactants decrease, concentration of products increase

Question 10

why do reactions slow down after some times

Answer 10

fewer reactants left to collide with

Question 11

Increase surface area in ror

Answer 11

increases chance of collisions which means more particles are exposed

Powdered solids react quicker than larger lumps

Question 12

Increase temp in ror

Answer 12

Particles get more energy and reach activation energy faster

Particle speed increases

Question 13

Adding a catalyst in ror

Answer 13

Provide an alternate pathway to travel with less activation energy

Catalyst remain unchanged both physically and chemically

Question 14

Why are catalysts widely used in the real world

Answer 14

Allow reaction to take place at lower temp
Saves energy
Have great economic importance in production
Are often enzymes
Can reduce pollution

Question 15

Increasing concentration of solution in ror

Answer 15

Results in more frequenct collisions

Low concentrasion = low collisions = slow ror

High concentration = high collisions = fast ror

Question 16

Increase pressure of gas in ror

Answer 16

Brings particles close together
increases frequency of collisons

More particles in a given volume = high pressure = frequent collisions = greater chance of reaction

Question 17

Application of factors affecting ror in the dangers of explosive combustion with fine powders and gases/ Also give example of such dangerous powders used in factories.

Answer 17

An explosion is a very fast reaction that releases a large volume of gaseous products. There is a danger of explosion in factories that handle powdered, flammable substances. These substances include custard powder, flour and powdered sulfur

Question 18

Reversible reactions

Answer 18

Both forward and the reverse reaction can occur as the product molecules can themselves react with each other or decompose and form the reactant molecules again.

Question 19

If the forward reaction is exothermic, the reverse will be

Answer 19

Endothermic as the same amount of heat is transferred in both directions.

Question 20

Equilibrium

Answer 20

A system is said to be in equilibrium when the rate of forward reaction is equal to the rate of the backward reaction and the concentration of reactant and product becomes constant in a reversible reaction in a closed system.

Question 21

More product than reactant, where does equilibrium lie?

Answer 21

Equilibrium lies to the right.

Question 22

More reactant than product, where does equilibrium lie?

Answer 22

Equilibrium lies to the left side.

Question 23

Types of equilibrium

Answer 23

Physical and Chemical.

Question 24

Physical equilibrium

Answer 24

If there is a physical change and only the state changes.

Question 25

Chemical equilibrium

Answer 25

If there is a chemical change and new substance is formed.

Question 26

Example of physical equilibrium reaction

Answer 26

Any hydrated salt breaking down into anhydrous salt + water.

Question 27

Le chatelier's principle

Answer 27

When a system in equilibrium is disturbed, the equilibrium wants to undo the disturbance to go back to equilibrium.

Question 28

What are the factors affecting equilibrium

Answer 28

Temperature, Pressure, Concentration, Catalyst.

Question 29

How does a change in temperature affect the equilibrium

Answer 29

Increasing the temperature shifts the equilibrium to endothermic side. Decreasing the temperature shifts the equilibrium to the exothermic side.

Question 30

How does a change in the pressure affect the equilibrium

Answer 30

Increase in pressure means number of particles per unit volume increase and hence equilibrium wants to go to side with less particles. Decreasing the pressure means the equilibrium will shift to the side with more gas molecules.

Question 31

3H₂ + N₂ ⇌ 2NH₃ where will the equilibrium shift

Answer 31

3 + 1 = 4 > 2. Hence equilibrium will shift in forward direction, increasing the yield of ammonia.

Question 32

How does a change in the concentration affect the equilibrium

Answer 32

Increasing the concentration of reactants/Decreasing concentration of products = equilibrium shifts in forward direction. Increasing concentration of products/Decreasing concentration of reactant = equilibrium shifts in reverse direction.

Question 33

How does adding a catalyst affect the equilibrium

Answer 33

Add a catalyst = increase rate of forward reaction and backward reaction in the same manner. Adding catalyst means equilibrium will be achieved faster, but they will have no effect on the yield of products/reactants.

Question 34

In an equilibrium graph, what happens to the lines of rate of forward and reverse reaction

Answer 34

The line representing rate of forward reaction gradually decreases before becoming constant. The line representing rate of reverse reaction gradually increases before becoming constant.

Question 35

What is the region called where the rate of forward and backward reactions are not constant, ie the region before equilibrium

Answer 35

Kinetic region.

Question 36

Haber's process

Answer 36

Industrial method for making ammonia (NH₃) from nitrogen (N₂) and hydrogen (H₂) gases at high pressure, moderate temperature and with a catalyst.

Question 37

Why is Haber process important in daily life

Answer 37

Haber process makes ammonia, which is an essential ingredient in the production of fertilizers, which helps grow the crops we eat.