21 Chemistry -- Chemical Equilibrium

What is meant by chemical equilibrium? Discuss the characteristics of chemical equilibrium.

1 Answers

Chemical equilibrium is the state of the system in which there is no observable change in the properties of system with time. The rate of forward reaction is equal to the rate of backward reaction and there is no change in the observable properties of the reaction system which is achieved only in a reversible reaction performed in a closed system.

The characteristics of chemical equilibrium are :-

Chemical equilibrium is dynamic in nature. When a reversible reaction has attained equilibrium condition, there is no further change in the composition of reaction mixture as the rate of forward reaction is equal to the rate of backward reaction.
Concentration of each of the reactants and products remains constant at equilibrium condition. This means the composition of system remains fixed at equilibrium condition.
The observable properties of the reaction system do not change with time at the equilibrium condition.
The equilibrium condition can be affected by the change in temperature and pressure.
The equilibrium condition can be achieved from any side.
The chemical equilibrium is possible only in a closed system because none of the reactants or products can escape. If the reaction is carried out in the open vessel, the heat produced is lost and the backward reaction does not take place.
The catalyst helps to attain equilibrium fast but it has no effect on the state of equilibrium because the catalyst changes the rate of forward and the backward reaction to the same extent.
A chemical equilibrium is characterized by a constant called equilibrium constant 'K'.

For the reaction CO+2H2 --------> CH3OHa. Kp > Kc b. Kp< Kc c. Kp =Kc d. Kp =Kc =0

Why is ammonia termed as a base although it does not have OH- ions in it?

One of the many reasons I would love to explain here is according to Lewis concept of bases.

The concept of acids, bases and salts, we have been discussing throughout the secondary education level was the Arrenhius Concept of Acids and Bases but which is not the only one describing these properties of compounds.

There are several other concepts such as:

Lewis concept of Acids and Bases
Bronsted-Lowry concept of Acids and Bases
Arrenhius concept of Acids and Bases

Lewis explains bases as the...

What is meant by concentration quotient of chemical reaction under what condition, it isequal to equilibrium constant?

The ratio of the product of concentrations of substances produced (products) to that of reactants is known as concentration quotient. It is denoted by Q. For example, for a reversible reaction. At equilibrium, Q becomes equal to K (equilibrium constant).

Can equilibrium be achieved between water and its vapor in an open beaker?

No, equilibrium cannot be achieved between water and its vapour in an open beaker. If one attempts to do so, he/she needs to maintain the equilibrium of water and vapour present in the given space.

Water vapour, being gas and lighter than air, rises up in the atmosphere and easily escapes away from the beaker. Thus, water vapour produced escapes into the surrounding and no equilibrium can be maintained between water and its vapour.

Why do we sweat more on a humid day?

Humidity is the measure of water vapor content in the air. Humidity also is reflected by dew point. Dew point is the temperatures air must be cooled in order to reach saturation.

When you have a high dew point which indicates more moisture present in the air, the body takes a longer time to naturally cool off.

The human body cools off by the process of evaporative cooling. Evaporative cooling is temperature reduction resulting from the evaporation of a liquid. Also, on a more scientific note,...

Why ice melts slowly at higher altitude?

For a given mass of water, ice has more volume than water. The atmospheric pressure is less or decreases at higher altitudes. On decreasing the pressure the equilibrium shifts to the side having more volume; the equilibrium shifts toward the formation of ice . It can be stated that on decreasing the pressure the freezing of water increases to form more ice so the melting of ice is favored at high temperature and high pressure. Hence, ice melts slowly at higher altitudes due to low pressure.

State and explain the law of mass action. Derive an expression for the equilibrium constantfor a reversible reaction.

The law of mass action is defined as at constant temperature , the rate of a forward reaction is directly proportional to the product of the molar concentration of the reactants each raised to a power equal to its stoichiometric coefficient that appear in the balanced chemical equation.For example , considerthe following general reaction; aA+ bB Products

Hence, according to the law, rate of reaction = k [A]^a[B]^b, where 'a' and 'b' represents the stoichiometric coefficient of reactants A and B...

State and explain Lichateliers principle and discuss its application.

1. Le-Chatelier's principle

Equilibrium state of a reversible reaction can be disturbed by changing temperature, pressure, volume and concentration of reaction system. This fact was thoroughly studied by a French Chemist Henry Louis Le-Chatelier in 1884. He made a generalization which is termed as Le-Chatelier's principle. This principle states that, ‘when a system in equilibrium is subjected to a change in temperature, pressure, volume and concentration, the equilibrium shifts in such a...

Derive the law of mass action for the expression:nA + mB------>pC + qD.

The dissociation of CaCO3 is suppressed at high pressure explain.

The dissociation of CaCO3 is suppressed at high pressure. In the above reaction, zero volume of reactants react to form the one volume of gaseous product CO2. With the increase in pressure, the equilibrium shifts towards the direction to decrease the volume. Since the left hand side has low volume so the reaction proceeds towards the left hand side. Hence the dissociation of CaCO3 is suppressed due to the addition reaction of CaO and CO2.

How does the solubility of a gas in liquid vary with pressure?

The solubility is a measure of the concentration of dissolved gas particles in a liquid and is the function of gas pressure. As you increase the pressure of the gas, the collision frequency increases and the solubility goes up. As you decrease the pressure, the solubility goes down due to decrease in collision frequency.

Study the equilibrium of the reactionPCI5(g)-------->PCl3 (g) + Cl2(g) --- HeatHow is the equilibrium of the reaction is affected by the temperature, pressure andintroduction of the chlorine gas?

Since the reaction is endothermic in forward direction, the increase in temperature shifts the equilibrium towards the forward direction whereas the decrease in temperature shifts the equilibrium towards the backward direction.

In the above equilibrium, one mole of reactant reacts to give two moles of product. So, equilibrium takes place by the increase in volume. Decrease in pressure shifts the equilibrium in the forward direction whereas the increase in pressure shifts the equilibrium in the...

For a reaction, A + B → 2C2 moles of A and 3 moles of B are allowed to react. If equilibrium constant is 4 at 400° C, then the mole of C at equilibrium is

What are the differences between Dynamic Equilibrium and Static Equilibrium?

The differences between dynamic equilibrium and static equilibrium are :-

Dynamic Equilibrium	Static Equilibrium
1. This type of equilibrium is irreversible in nature.	1. This type of equilibrium is irreversible in nature.
2. In dynamic equilibrium, the forward and backward reaction rates are equal .	2. In static equilibrium, the forward and backward reaction rates are zero.
3. This equilibrium implies that reactants and products are still participating in chemical...

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