Thermodynamics class 11 chemistry chapter 6

ap chemistry thermodynamics || What is Irreversible process || What are the Mode of exchange of energy || What is the Specific heat capacity || What is the Sign of Heat || What are the Laws of Thermodynamics || What is the enthalpy 

2. What is an Irreversible process?

• Thermodynamics process which takes finite Time and a single step to complete is called the Irreversible process.

• In this process maximum work is not done.

• It is an algebraic form for the Calculation of work done.

• Difference between the driving force and opposing force is very large.

Internal energy:-It is a sum of all kinds of energy present in a system.

Denoted by:- E or U

E=U=P.E+K.E. + vibrational energy+ rotational...etc.

*Absolute internal energy is not calculated

•Change in internal energy is calculated.

•Change in internal energy is a State function.

•Change in internal energy.

•In the cyclic process internal energy is zero.

•Internal energy is changed by work done, heat, exchange of matter.

What are the Mode of exchange of energy?

Work is in many types like 

1) Electrical work=V.Q.=V × it= i²Rt (Q=it V=iR)

2) Mechanical work=p×delta×V

Signs:- 

1. Work done by the system (expansion)=

Work takes in  - ( minus sign)

2. Work done on the system (contraction)=

Work takes in + (plus sign)

2. Heat 

When the exchange of energy takes place and a temperature difference arises this exchange of energy is called Heat. It is denoted by small ' a.

It is directly proportional to the mass of the substance as well as the temperature difference.

Heat(q) Directly proportional to mass ×∆temperature

q=m×C∆t [°•°C=specific heat capacity]

What is the Specific heat capacity?

The amount of heat that is needed to raise the temperature from 1° to 1kg mass of a substance is called the Mass of substance. At this stage numerical value of heat and specific heat capacity are equal.

Unit of specific heat capacity

q=m×C∆t

=)Joule=kg×C×k

=)C=joule kg-¹ k-¹

q=n×C∆t   [°•°n=mole]

•°•C= molar heat capacity

Amount of heat required to raise temperature 1° to 1 mole of a substance. This amount of heat is numerically equal to molar heat capacity.

q=nC∆t

Where,

n=no. of mole

C=molar heat capacity

∆t=change in temperature 🌡️

Unit if Molar heat capacity

q= nC∆t

C=joule mole-¹ k-¹

What is the Sign of Heat?

If heat is given by the system. It is taken negatively.

If heat is taken by the system. It is taken positively.

Unit of Heat 

1. Calorie (CGS Unit)

The amount of heat which is needed to raise temperature 1°(13•5°-14•5°) is called 1 calorie.

1 calorie= 4•18 joule

Joule is an SI unit 

What are the Laws of Thermodynamics?

Thermodynamics follows some laws. This is called the law of Thermodynamics.

i. ZLOT:-Zeroth law of Thermodynamics

ii. FLOT:- First law of thermodynamics

iii. SLOT:- Second law of thermodynamics

iv. TLOT:- Third law of Thermodynamics

1. ZLOT:- 

•It is related to thermal equilibrium.

•Thermal equilibrium is the stage at Which no flow of heat takes place. 

•At thermal equilibrium there is no temperature difference.

•At thermal equilibrium temperature difference is zero.

If system A thermal equilibrium with B. B is thermal equilibrium with C then A must be thermal equilibrium with C.

FLOT:- First law of thermodynamics

Based on conservation of energy

•energy of the universe is conserved.

•Energy can be neither be created nor be destroyed only transformation takes place.

Mathematical Definition

Change in internal energy is equal to the sum of Heat and work. Mathematically,

Change in internal energy (∆U=∆E)=Heat(q) + work(w),

∆U=q+w

What is enthalpy?

It is a new thermodynamics factor that is equal to internal energy and pressure-volume work.

H=E + PV

Absolute internal energy is not measured, only change in internal energy is measured. So, only we calculate the change in enthalpy.

∆H=∆E+P∆V

In chemistry

∆H=∆E+∆ngRT

 °•°∆ng=mole of product - mole of reactant

∆H= - exothermic

∆H= + endothermic

∆H= 0 Nothermic

Heat capacity

The amount of heat that is needed to raise temperature 🌡️ 1 ° to a given mass of a substance is called heat capacity.

Heat (q) = heat capacity × ∆T

q= C∆T

C denoted Heat capacity

Types of Heat capacity

1. Cp:- Heat capacity at constant pressure.

2. Cv:- Heat capacity at constant volume.

1. Qv=Cv∆t

2. Qp= Cp∆t

Constant volume

P∆V= P× 0=0=Work

FLOT=

∆E=q+w

∆E=q=Qv

Heat at constant pressure is equal to enthalpy change∆H at heat at constant volume is equal to change in internal energy.

From definitions of enthalpy change

∆H=∆E+P∆V

Qp=qv+P∆V

For 1 mole of an ideal gas 

PV=RT

P∆V=R∆T

CP∆T= Cv∆t + R∆T

Cp=CV + R

All remaining parts read in the next part 

Next part 👉What is the definition of thermochemistry

Thanks for reading 💕

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