C4.2 Reaction rates and Reversible Reactions

1. State Le Chatelier’s Principle

It states that when a change in conditions is applied to a system in equilibrium, the system moves so as to oppose that change

When a change in conditions is applied to a reversible reaction system, the system moves so as to oppose that change.

When a change in conditions is applied to a system in un-equilibrium, the system moves so as to oppose that change.

None of the mentioned

2. What is the effect of temperature on the rate of reaction?

Rate of reaction increases with a rise in temperature

An increase in temperature increases the kinetic energy of the particles

An increase in kinetic energy makes the particles to move faster and collide more frequently with sufficient energy to cause more effective collisions per given time

All of the above

3. How does the amount of time taken affect the rate of reaction?

The rate of reaction is inversely proportional to the time taken for the whole reaction to occur

Rate of reaction is directly proportional to the time taken

The rate of production of the products during the reaction is high at the start but eventually decreases and stops when all reactants are used up

Both A and C

4. What is the effect of surface area on the rate of reaction?

An increase in surface area of the particles thus increasing the area of contact of the reacting particles

The greater the surface area of contact between reacting particles the higher the rate of reaction

An increase in the surface area decreases the rate of reaction

Both A and B

5. What do you expect when you add up a catalyst such as Manganese (IV) oxide in a chemical reaction?

The mass of Manganese (IV) Oxide remains the same

The catalyst remains chemically unchanged

It will provide a shorter route for reactions thus minimizing the energy required for reactions to start

All of the above

6. A change in pressure will only affect equilibrium in reactions involving gases. True or False

FALSE

Maybe

TRUE

Maybe

7. The reaction rate is a measure of how much of the reactions are consumed or how much of the products are formed per unit time. True or False

FALSE

Maybe

TRUE

None

8. Define reversible reactions

It is a chemical reaction that can proceed in either direction by changing certain conditions.

There are two directions in the reaction, The forward and reverse direction which is represented by double arrows i.e. NH4Cl(S) -NH3(g) + HCl(g)

The forward direction is associated with thermal dissociation and the reverse direction is associated with recombination

All of the above

9. Mention the factors affecting the rate of reaction

The concentration of reactant and Time taken for the reaction to occur.

Temperature and surface area of contact between reactants

Addition of catalyst and the presence of light on the reaction

All of the above

10. When the concentration of the particles of the reactants is high how does it affect the rate of reaction

The number of collisions will be high

The number of successful collisions will increase

An increase in the rate of reaction

All of the above

11. How does the change in concentration affect equilibrium?

When a change in conditions is applied to a system in equilibrium, the system moves so as to oppose that change.

If the concentration of B is increased then the reaction will favor the direction which helps in reducing the concentration of B. This achieved by reacting more of B to form C and D as follows:- A(aq) + B(aq) , C(aq) + D(aq)

If the concentration of D is increased then the backward reaction will be favored which helps in reducing the concentration of D. This achieved by reacting more of D to form A and B.

all of the above

12. A change in pressure has no effect on those reactions in which both reactants and products are either solids or liquids even if they are in an equilibrium state. True or False

TRUE

FALSE

Maybe

None

13. Define optimum conditions

It states that when a change in conditions is applied to a system in equilibrium, the system moves so as to oppose that change.

The minimum energy required by the reacting particles to cause a successful collision to form products

The conditions required to obtain the highest yield of the products in the shortest time at minimum cost

None of the mentioned.

14. What is the effect of pressure on the rate of reaction of a solid and liquid chemical reaction?

Pressure increases the rate of chemical reaction of solids and liquids.

Pressure decreases the rate of chemical reaction of solids and liquids.

It has no effect all on the chemical reaction of solids and liquids

None of the mentioned

15. What is the effect of pressure on the rate of reaction of a gas chemical reaction?

Pressure increases the rate of chemical reaction of gas.

Pressure decreases the rate of chemical reaction of gas

it has no effect all on the chemical reaction of gas

None of the mentioned

16. Define Collision Theory

In order for a reaction to occur reacting particles must collide but not all collision results into products

In order for a reaction to occur reacting particles must collide and all collision results into products.

In order for a reaction to occur products must react to form reactants

None of the mentioned

17. A substance that alters the rate of reaction of a chemical reaction but remains chemically unchanged at the end of the reaction is called?

Booster

Manganese (IV) oxide

catalyst

None of the mentioned

18. A catalyst has no effect on the position of equilibrium it only alters the rate at which the equilibrium is attained. True or False

FALSE

Maybe

TRUE

None

19. Discuss photochemical reactions

Processing of photographic plates made of Silver bromide is only done in the dark to avoid decomposition of silver bromide

The reaction between Chlorine and hydrogen to give hydrogen chloride gas is done only in the presence of light, similar to the reaction of bromine and methane which only occurs in light.

Photosynthesis occurs only in the presence of light where carbon (IV) oxide and water are converted to sugar

All of the above

20. What is the effect of adding a catalyst such as Manganese (IV) oxide to the rate of reaction?

The addition of a catalyst such as Manganese (IV) Oxide makes the rate of reaction faster

The catalyst is not used up during the reaction but it alters the rate of the chemical reaction

A catalyst works by lowering the activation energy of the reaction

All of the above

21. Explain the reason why a change in pressure has no effect on those reactions in which both reactants and products are either solids or liquids

Solids and liquids can be compressed

Solids and liquids can be expanded

Solids and liquids cannot be compressed or expanded.

None of the mentioned.

22. What is the effect of light on the rate of reaction?

Light energy energies some of the particles involved in the chemical reactions such as Silver bromide

Light energy increases the number of effective collisions per unit time thus increasing the rate of reaction

Silver bromide in the presence of light energy decomposes to metallic silver and bromine

All of the above

23. What is the effect of change of temperature on equilibrium

An increase in temperature will favor the process that absorbs heat [ endothermic]

A decrease in temperature will favor the process that generates heat { exothermic}

A change in temperature alters the position of a chemical equilibrium

All of the above

24. How does pressure affect a system of gas which is in equilibrium?

If the pressure of a system in equilibrium is increased the system will favor the direction that has fewer molecules

Applying more pressure will favor the direction of reaction which will reduce the pressure.(which has few molecules

Decreasing pressure will favor a direction of reaction which will increase pressure ( which has more molecules)

All of the above

25. Mention the factors which affect Equilibrium

Temperature

Pressure

Concentration

All of the above

26. The minimum energy required by the reacting particles to cause a successful collision to form products is referred to as

Collision Threshold

Minimum energy

Activation energy

Activation key

27. Mention some of the properties which are observed when reactants are consumed to form products per unit time

Change in mass

Volume in the gas produced

The intensity of the color of the products produced

All of the above

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