The rate and extent of chemical change

Question 1

How can you calculate the rate of reaction?

Answer 1

Rate of reaction = amount of reactant used
————————————-
Time

Rate of reaction = amount of product formed
————————————–
Time

Question 2

What factors affect the rates of chemical reactions?

Answer 2

o concentration
o pressure
o surface area
o temperature
o catalysts

Question 3

What is collision theory?

Answer 3

chemical reactions can occur only when reacting particles collide with each other and with sufficient energy.

Question 4

What is activation energy?

Answer 4

The minimum amount of energy that particles must have to react.

Question 5

What will happen in a chemical reaction if you increase the concentration?

Answer 5

Increasing the concentration of reactants in solution, the pressure of reacting gases, and the surface area of solid reactants increases the frequency of
collisions and so increases the rate of reaction.

Question 6

What will happen in a chemical reaction if you increase the temperature?

Answer 6

Increasing the temperature increases the frequency of collisions and makes the collisions more energetic, and so increases the rate of reaction.

Question 7

What are catalysts?

Answer 7

Catalysts are substances that speed up chemical reactions without being changed or used up during the reaction.

Question 8

What acts a catalysts?

Answer 8

Enzymes act as catalysts in biological systems.

Question 9

How do catalysts speed up the reaction?

Answer 9

● Catalysts decrease the activation energy;
this increases the proportion of particles with
energy to react.
● Catalysts provide a different pathway for a
chemical reaction that has a lower activation
energy.

Question 10

How does the surface area affect the rate of reaction?

Answer 10

1) Small pieces of a solid reactant have a large surface area in relation to their volume.
2) More particles are exposed and available for collisions, so there are more collisions and a faster reaction.

Question 11

What is the sample of the practical of the rate of reaction?

Answer 11

MAKE A SKETCH OF THE PRACTICAL FIRST

1) Set up the equipment as shown.
2) Add the hydrochloric acid to the flask and swirl to mix the reactants.
3) Start the timer.
4) Watch the cross through the flask.
5) When the cross is no longer visible stop the timer.
6) Repeat the experiment using hydrochloric acid of a different concentration.

Question 12

What are the variable for this practical?

Answer 12

Independent variable - Concentration of the acid
Dependent variable - The time it takes for the cross to disappear
Control variable - Volume of the acid

Question 13

When does a reversible reaction occur?

Answer 13

When the products of the reaction can react to produce the original reactants.

Question 14

how can the direction of the reversible reactions be changed?

Answer 14

The direction of reversible reactions can be changed by changing the conditions.

Question 15

When does the same amount of energy be transferred in each case?

Answer 15

If a reversible reaction is exothermic in one direction, it is endothermic in the opposite direction. The same amount of energy is transferred in each case.

Question 16

How do you calculate the concentration of a reactant?

Answer 16

Concentration = Mol : Volume (dm^3)

Question 17

What happens to the reactants as the reaction progresses?

Answer 17

The reactant gets used up so the amount of reactant decreases.

Question 18

What happens in a closed system?

Answer 18

No reactants are added and no products are removed.

Question 19

What happens when a reversible reaction occurs in a closed system?

Answer 19

An equilibrium is achieved When the rate of the forward reaction is equal to the rate of the backward reaction.

Question 20

What is Le Chatelier’s Principle?

Answer 20

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

Question 21

What is the effect on the equilibrium if the concentration of one of the products or reactants is changed?

Answer 21

*If the concentration of one of the reactants or products is changed,
the system is no longer at equilibrium and the concentrations of all
the substances will change until equilibrium is reached again.

*If the concentration of a reactant is increased, more products will be
formed until equilibrium is reached again.

*If the concentration of a product is decreased, more reactants will
react until equilibrium is reached again

Question 22

What is the effect on the equilibrium if the temperature is increased?

Answer 22

• The relative amount of products at equilibrium increases for an
  endothermic reaction.
• The relative amount of products at equilibrium decreases for
  an exothermic reaction.

Question 23

What is the effect on the equilibrium if the temperature decreases?

Answer 23

The relative amount of products at equilibrium decreases for
an endothermic reaction

The relative amount of products at equilibrium increases for an
exothermic reaction.

Question 24

What happens to the equilibrium if we increase the pressure in gaseous
reactions?

Answer 24

An increase in pressure causes the equilibrium position to shift towards the side with the smaller number of molecules as shown by the symbol equation for that reaction.

Question 25

hat happens to the equilibrium if we increase the pressure in gaseous reactions?

Answer 25

A decrease in pressure causes the equilibrium position to shift towards the side with the larger number of molecules as shown by the symbol equation for that reaction.