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Physical Chemistry (NK) > Chemical Equilibrium > Flashcards

Chemical Equilibrium Flashcards

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1
Q

What is thermochemistry?

A

It deals with the measurement or calculation of heat absorbed or given out during a chemical reaction.

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2
Q

What are the units of energy?

A

The units of energy are calorie and kilocalorie. However, this is not the SI units of energy.

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3
Q

SI units of energy?

A

Joules and Kilo joules.

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4
Q

1 Calorie = how many joules?

A

1 calorie = 4.184 J

1 Joules = 0.239 calorie

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5
Q

What is Equilibrium state?

A

When the rate of forward reaction as well as reverse reaction occur at the same rate to maintain the equilibrium position of the chemical reaction, this balance is called equilibrium state.

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6
Q

What are the types of equilibrium?

A
  1. Static equilibrium: at rest, no external force acting upon it. not moving unless an external force acts upon it.
  2. Dynamic equilibrium: is moving with constant speed and velocity. will not change until acted upon by an external force.
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7
Q

Does value of kc depends upon initial concentration of the reactants?

A

No. The value of Kc depends upon the equilibrium conc. of the reactants.

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8
Q

Why do we use Kp for gases instead of Kc?

A

Because, at a given temperature, the partial pressure of the gas is proportional to the concentration of the gas. So we use Kp for partial pressure instead of using Kc for gases.

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9
Q

Which phenomenon constantly changes the value of kc in a closed system?

A

Temperature.

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10
Q

What does Kc of a reaction tell us?

A
  • the extent of the reaction
  • the direction of the reaction
  • the yield of the reaction
  • where the equilibrium lies
  • quality and quantity of the product produced
  • the time of the reaction
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11
Q

Catalyst changes the value of Kc?

A

No. It just helps to reach the equilibrium quicker.

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12
Q

kc = 0 possible?

A

No.

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13
Q

Unit of Kc?

A

moles\L

moles\dm-3

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14
Q

exothermic direction for reactions when temperature is changed.

A

exothermic increase backward

exothermic decrease forward

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15
Q

What does the value of kc tell us when it is too small?

A

Small kc means the concentration of the reactant (in denominator) is higher than the product so the kc will move in the opposite direction. reaction will move forward.

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16
Q

What does higher value of kc tell us?

A

The higher value of kc tell us that the concentration of product (in numerator) is higher than the reactant. the reaction will move in the backward direction to maintain the equilibrium.

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17
Q

What does the pressure of the reaction depend upon?

A

Volume ration of the product and reactant.

18
Q

In terms of pressure, when does the direction of the reaction shift towards left?

A

When the volume of the product is higher than the volume of the reactant.

19
Q

In terms of pressure, when the direction of the reaction shift towards right?

A

When the volume of the reactant is greater than the volume of the product, the reaction shifts towards right, in the direction of the product.

20
Q

Why we check volume to calculate the relation between kc and kp?

A

Because kp is partial pressure of the gas and for pressures we check volume.

21
Q

When is kc equal to kp?

A

When there is no change in volume.
Example:
1:1 , 2:2

22
Q

When is kc > kp?

A

When the volume of the product is greater than the reactant then kc will be greater than kp.

23
Q

when is kp > kc?

A

When the volume of reactant is greater than the volume of the product, kc will be less than kp.

24
Q

What are the factors that affect the rate of reaction according to Le Chatelier’s principle?

A
  1. Concentration
  2. Pressure
  3. Temperature
25
Q

What does Le Chatelier Principle say?

A

“When a stress or constraint is applied in the direction of the system in equilibrium, the system opposes this change and the equilibrium position changes so as to undo the constraint.”

26
Q

What happens when we increase the concentration of a reactant in a chemical reaction?

A

The reaction moves towards right.

27
Q

What happens when the concentration of the product is increased?

A

Reaction shifts towards left. in the direction of the reactant.

28
Q

Advantage of increasing the concentration of reactants?

A

Higher yield of product at cheaper rates for industries.

29
Q

Le Chatelier’s principle in terms of temperature?

A
  1. exothermic increase backward 1. endothermic increase
    forward (favors high yield of
    product)
  2. exothermic decrease forward 2. endothermic decrease
    backwards
30
Q

Why is pressure change a gaseous phenomenon?

A

Because pressure does not affect solids and liquids as much as it affects gases. It depends upon volume.

31
Q

Le Chatelier’s affect on pressure changes?

A

volume of product higher - reaction moves backwards

volume of reactant higher - reaction moves forwards

32
Q

Does catalyst have any affect on equilibrium of the reaction?

A

No. It. Does. Not.

33
Q

What are the applications of Le Chatelier’s principle?

A
  1. Contact process - sulfuric acid, exothermic, decrease in volume, catalyst used vanadium.
  2. Harbor’s process - ammonia, exothermic, decrease in volume,
34
Q

What is ksp?

A

product of the dissolved ions of the sparingly soluble salts. It also varies with temperature.

35
Q

What is heterogenous equilibria?

A

When the products and reactants are in more than one phase that is gases, liquid and gas then it is said to be heterogenous equilibria.

36
Q

Effect of catalyst on speed of reaction?

A

Increases.

37
Q

Effect of pressure on speed?

A

Direct relation.

38
Q

Effect of temperature on speed of reaction?

A

direct relation.

39
Q

Effect of concentration on speed?

A

Direct relation.

40
Q

precipitation occurs when the ionic concentration is

A

More than ksp.

41
Q

precipitation does not occur when

A

ksp (solubility product) is larger than the ionic product.

Physical Chemistry (NK) (3 decks)

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