Laws of Thermodynamics Equilibrium

THERMODYNAMIC EQUILIBRIUM (थायरोडायनामिक एक्विलिब्रियम)

Equilibrium Expressions

Equilibrium Constant Expressions	Rules for Writing Equilibrium Constant Expressions	Altering or Combining Equilibrium Reactions
Reaction Quotients: A Way to Decide Whether a Reaction is at Equilibrium	Changes in Concentration that Occur as a Reaction Comes to Equilibrium	Hidden Assumptions that Make Equilibrium Calculations Easier
A Rule of Thumb for Testing the Validity of Assumptions	What Do We Do When the Approximation Fails?	Equilibria Expressed in Partial Pressures
The Effect of Temperature on a Chemical Reaction

            A system is said to exist in a state of thermodynamic equilibrium when no change in any macroscopic property is registered, if the system is isolated from its surroundings
         
            An isolated system always reaches in course of time a state of thermodynamic equilibrium and can never depart from it spontaneously .
            Therefore, there can be no spontaneous change in any macroscopic property if the system exists in an properties of physical systems that are found in equilibrium states .
            A system will be in a state of thermodynamic equilibrium, if the conditions for the following three types of equilibrium are satisfied:

(a) Mechanical equilibrium
(b) Chemical equilibrium
(c) Thermal equilibrium

(ए) मैकेनिकल संतुलन

(b) रासायनिक संतुलन

(c) थर्मल संतुलन


           In the absence of any unbalanced force within the system itself and also between the system and the surroundings, the system is said to be in a state of mechanical equilibrium. If an unbalanced force exists, either the system alone or both the system and the surroundings will undergo a change of state till mechanical equilibrium is attained.
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(सिस्टम के भीतर और सिस्टम और परिवेश के बीच किसी भी असंतुलित बल की अनुपस्थिति में, सिस्टम को यांत्रिक संतुलन की स्थिति में कहा जाता है। यदि कोई असंतुलित बल मौजूद है, तो या तो प्रणाली या दोनों प्रणाली और परिवेश यांत्रिक संतुलन प्राप्त होने तक राज्य के परिवर्तन से गुजरेंगे।)

           If there is no chemical reaction or transfer of matter from one part of the system to another, such as diffusion or solution, the system is said to exist in a state of chemical equilibrium equilibrium state. Thermodynamics studies mainly the

           When a system existing in mechanical and chemical equilibrium is separated from its surroundings by a diathermic wall (diathermic means 'which allows heat to flow') and if there is no spontaneous change in any property of the system, the system is said to exist in a state of thermal equilibrium. When this is not satisfied, the system will undergo a change of state till thermal equilibrium is restored
           When the conditions for any one of the three types of equilibrium are not satisfied, a system is said to be in a nonequilibrium state. If the nonequilibrium of the is due to an unbalanced force in the interior of a system or between the system and the surroundings, the pressure varies from one part of the system to another. There is no single pressure that refers to the system as a whole. Similarly if the nonequilibrium is because of the temperature of the system being different from that of its surroundings, there is a nonuniform temperature distribution set up within the system and there is no single temperature that stands for the system as a whole. It can thus be inferred that when the conditions for thermodynamic equilibrium are not satisfied, the states passed through by a system cannot be described by thermodynamic properties which represent the system as a whole.
             Thermodynamic properties are the macroscopic coordinates defined for, and significant to, only thermodynamic equilibrium states. Both classical and statistical thermodynamics study mainly the equilibrium states of a system.
(थर्मोडायनामिक गुण स्थैतिक निर्देशांक हैं, और केवल थर्मोडायनामिक संतुलन राज्यों के लिए महत्वपूर्ण हैं। शास्त्रीय और सांख्यिकीय दोनों थर्मोडायनामिक्स मुख्य रूप से एक प्रणाली के संतुलन राज्यों का अध्ययन करते हैं।)





           In a balanced chemical equation, the total number of atoms of each element present is the same on both sides of the equation. Stoichiometric coefficients are the coefficients required to balance a chemical equation. These are important because they relate the amounts of reactants used and products formed. The coefficients relate to the equilibrium constants because they are used to calculate them. For this reason, it is important to understand how to balance an equation before using the equation to calculate equilibrium constants.

Introduction

There are several important rules for balancing an equation:

1. An equation can be balanced only by adjusting the coefficients.
2. The equation must include only the reactants and products that participate in the reaction.
3. Never change the equation in order to balance it.
4. If an element occurs in only one compound on each side of the equation, try balancing this element first.
5. When one element exists as a free element, balance this element last.

Example 1:

H2(g)+O2(g)⇌H2O(l)$$H_2(g)+O_2(g)\rightleftharpoons H_{2}O(l)$$

Because both reactants are in their elemental forms, they can be balanced in either order. Consider oxygen first. There are two atoms on the left and one on the right. Multiply the right by 2	H2(g)+O2(g)⇌2H2O(l)$$H_2(g)+O_2(g)\rightleftharpoons 2H_{2}O(l)$$
Next, balance hydrogen. There are 4 atoms on the right, and only 2 atoms on the left. Multiply the hydrogen on left by 2	2H2(g)+O2(g)⇌2H2O(l)$$2H_2(g)+O_2(g)\rightleftharpoons 2H_{2}O(l)$$
Check the stoichiometry. Hydrogen: on the left, 2 x 2 = 4; on right 2 x 2= 4. Oxygen: on the left: 1 x 2 = 2; on the right 2 x 1 = 2 . All atoms balance, so the equation is properly balanced.	2H2(g)+O2(g)⇌2H2O(l)$$2H_2(g)+O_2(g)\rightleftharpoons 2H_{2}O(l)$$

Example 
$2$:

Al(s)+MnSO4(aq)⇌Al2(SO4)3+Mn;(s)$$Al(s)+MnS{O}_4(aq)\rightleftharpoons A{l}_2(S{O}_4{)}_3+Mn;(s)$$

First, consider the SO42- ions. There is one on the left side of the equation, and three on the right side. Add a coefficient of three to the left side.	Al(s)+3MnSO4(aq)⇌Al2(SO4)3+Mn(s)$$Al(s)+3MnS{O}_4(aq)\rightleftharpoons A{l}_2(S{O}_4{)}_3+Mn(s)$$
Next, check the Mn atoms. There is one on the right side, but now there are three on the left side from the previous adjustment. Add a coefficient of three on the right side.	Al(s)+3MnSO4(aq)⇌Al2(SO4)3+3Mn(s)$$Al(s)+3MnS{O}_4(aq)\rightleftharpoons A{l}_2(S{O}_4{)}_3+3Mn(s)$$
Consider Al. There is one atom on the left side and two on the right side. Add a coefficient of two on the left side. Make sure there are equal numbers of each atom on each side.	2Al(s)+3MnSO4(aq)⇌Al2(SO4)3+3Mn(s)$$2Al(s)+3MnS{O}_4(aq)\rightleftharpoons A{l}_2(S{O}_4{)}_3+3Mn(s)$$