C8 Rates and Equilibium

Question 1

How to find the rate of a reaction

Answer 1

Monitoring the amount of reactants used up over time

Or measuring the amount of products over time

Question 2

How to find the rate of reaction on a graph

Answer 2

Find the gradient of a line

Draw a tangent to the curve

Question 3

What is activation energy

Answer 3

The minimum amount of energy that particles must have in order to react, they must collide with a certain amount of energy before they can react

Question 4

How does the size of the particles change the rate of reaction

Answer 4

The rate of a reaction increases if the surface area to volume ratio of the solid reactant increases, this increases the frequency of collisions between the particles

Question 5

How do you increase the rate of reaction

Answer 5

Increase the frequency of reacting particles colliding with eachother
Increase the energy they have when they collide
Increase surface area : volume ratio to increase frequency of collisions

Question 6

What is the equation for the mean rate

Answer 6

Mass of reactant used up (g)/ time

Question 7

Why does increasing the temperature increase the rate of reaaction

Answer 7

Increasing the temperature increases the rate of reaction because particles collide more frequent and more energetically. More of the collisions ocurring in a given time results in a faster reaction because a higher proportion of particles have energy greater than the activation energy

Question 8

How does concentration increase the rate of reaction

Answer 8

Infreasing the concentration of reactants in solution increases the frequency of collisions between particles and so increases rate of reaction

Question 9

How does increasing the pressure change the rate of reaction

Answer 9

Increasing the pressure of reacting gases increases the frequency of collisions because the gas particles are moving faster this increases the rate of reaction

Question 10

What is the lab test for oxygen

Answer 10

Relights a glowing splint

Question 11

What is a catalyst

Answer 11

A chemical substance that speeds up a chemical reaction by decreasing the activation energy. It is not used up itself during the reaction

Question 12

How can catalysts stop working in industry

Answer 12

Catalysts used in chemical plants can become ‘ poisoned ‘, and not work anymore. This happens because impurities in the reaction mixture combine with the catalyst and stop it working

Question 13

What are the benefits of catalysts in industry

Answer 13

They increase the rate of reaction and reduce energy costs which maximises profits

Question 14

What happens to the catakyst in a symbol equation

Answer 14

We do not include the catalyst as a reactant in a symbol equation, instead it goes above/ below the arrow leading to the products

Question 15

What is an example of a reaction that includes a catalyst

Answer 15

2H2O2 -(catalyst)–> 2H2O + O2

Catalyst is mangenese dioxide ( MNO2 )

Question 16

What is the lab test for water

Answer 16

White anhydrous copper sulphate turns blue

Cobalt chloride paper turns from blue to pink

Question 17

What js the general formula for a reversible reaction showing the forwards and reverse reaction

Answer 17

Forwards reaction : A+B ⇌ C+D

Reverse reaction: C+D⇌A+B

Question 18

What is the rule with energy changes in a reversible reaction

Answer 18

The reaction one way is exothermic and the reverse is endothermic

Question 19

What is the rule with the amount of energy transferred in a reversible reaction

Answer 19

In any reversible reaction, the amount of energy transferred to the surroundings when the reaction goes one way is exactly equal to the energy transferred back when the reaction goes in the opposite direction

Question 20

How would a reaction profile show a reversible reaction

Answer 20

The difference in energy between the reactants and the products will be the same for both directions of the reaction. Reaction profiles can also be used to determine which direction of the reaction is exothermic or endothermic

Question 21

When does equilibrium occur in a chemical reaction

Answer 21

Equilibrium occurs when the reaction is in apparatus which prevents the escape of reactants and products. Equilibrium is achieved when the forwards and reverse reactions occur at exactly the same rate

Question 22

What is Le Châtelier’s principle

Answer 22

If you change a componet in a reaction that is in dynamic equilibrium, the reaction will adjust and shift the position of equilibrium to cancel out the change and return to dynamic equilibrium

Question 23

According to LC princple what would happen if the product of the forwards reaction is decreased

Answer 23

If the product of the forwards reaction is decreased, the forwards reaction will increase in rate ( equilbrium shifts ) to make more of the product

Question 24

How does temperature effect the amount of products formed in the forwards reaction

Answer 24

If forwards reaction is Exothermic:
Increase - less products formed - reaction goes to endothermic to decrease temp( more reactants )
Decrease - more products formed - reaction goes to exothermic to increase temp ( less reactant )

If forwards reaction is Endothermic:
Increase - more products formed - reaction goes more endothermic to cool the temperature
Decrease - less products formed - reaction goes more exothermic to raise the temperature

Question 25

How does pressure effect the amount of products in the forwards reaction of a reversible reaction

Answer 25

If forwards reaction produces more molecules of gas
Increase - decrease products
Decrease - increase the products

If forwards reaction produces less molecules of gas
Increase - increase products
Decrease - decrease products

Question 26

What is the word equation for the Haber Process

Answer 26

Nitrogen + hydrogen = ammonia

Question 27

Symbol equation for the haber process

Answer 27

N2(g) + 3H2(g) = 2NH3(g)

Question 28

Where are the reactsnts for the haber processes obtained

Answer 28

Nitrogen: liquifying air
Hydrogen: from natural gas ( mainly methane ): methane + steam = hydrogen + carbon dioxide

Question 29

What are the conditions for the Haber process and why are they those values

Answer 29

Pressure: 200 atmospheres, any higher pressure would cost money to make structurally sound
Temperature: 450°C, a temp lower would be better but reaction would be too slow
Catalyst: iron filings, higher surface area to volume ratio