Lecture 8

Question 1

What is activation energy?

Answer 1

Is the minimum amount of energy needed to start a chemical reaction. All chemical reactions need a certain amount of activation energy to get started.

Question 2

What is an exothermic reaction?

Answer 2

At the end of the reaction the products have less energy than the reactants, as there is a release of energy.

Question 3

What is an endothermic reaction?

Answer 3

The reaction continually absorbs energy to keep going. The energy of the products is greater than the energy of the reactants.

Question 4

What factors affect the activation energy?

Answer 4

The nature of the reactant= ionic reactant activation energy will be low as there is an attraction between reacting species.
Catalyst: positive provides an alternative path where the activation energy is lower. Negative catalyst provides a higher activation energy.

Question 5

Whats the formula for Activation Energy?

Answer 5

K = Ae-Ea/RT

Question 6

How do you get the formula for ln(k1/k2)

Answer 6

Taking natural log on both sides
ln k = ln A − Ea.RT
Then make Ea the subject of the formula and solve the equation
Subtract lnk2 from lnk1

Question 7

What is the difference between activation energy and energy?

Answer 7

Activation energy is the minimum amount of extra energy required by a reacting molecule to get converted into product. Free energy is the amount of energy available for a thermodynamic system to perform thermodynamic work.

Question 8

What is high activation energy?

Answer 8

A significant amount of energy must be added to the system before the reaction can proceed. This can make the reaction slower or more difficult to initiate. This is because molecules can only complete the reaction once they have reached the top of the activation energy barrier.

Question 9

What factors affect the rate of reactions?

Answer 9

Surface area
Temp
Pressure
Concentration
Catalysts
Enzymes
Solvent
Order
Electromagnetic Radiation

Question 10

How does surface area affect the rate?

Answer 10

If solid is broken into smaller pieces, more particles are exposed to the surface and the reaction happens quicker.

Question 11

How does temp effect the rate?

Answer 11

Temp increases, particles accelerate, particles have more energy= which helps reactants get over the activation energy barrier more quickly.

Question 12

How does pressure effect the rate?

Answer 12

Pressure increases the concentration of gas increases= rate of reaction increases.

Question 13

How does a catalyst effect the rate of change of a reaction?

Answer 13

Catalyst introduce alternative reaction pathways with significantly lower activation energies. More molecules are able to take part in fruitful collisions.

Question 14

What is an example of a catalyst?

Answer 14

In the haber process an iron catalyst is sued to increase the rate.
3H2+N2=2NH3

Question 15

What is an inhibitor?

Answer 15

A material used to decrease the rate of a chemical reaction.

Question 16

What is an example of an inhibitor?

Answer 16

Preservatives are added to food to prevent spoiling.

Question 17

What is an enzyme?

Answer 17

Enzymes are biological catalysts. They are large protein molecules which enable the biochemical reactions that happen in living things to take place very quickly at relatively low temps.

Question 18

The rate of chemical reaction depends on the nature of reactants, why?

Answer 18

Because it determines the strength and frequency of the chemical bonds that need to be broken and formed during the reaction. Reactants that have stronger bonds require more energy to be broken, which can slow down the reaction rate.