Laws Of Thermodynamics.

Question 1

What is molar heat capacity ?

Answer 1

Molar heat capacity is the heat required to raise the temperature of 1 mole of any substance by 1 C or 1 K.
It’s denoted by C.

Question 2

What is the formula of molar heat capacity ?

Answer 2

Q= nC(T’-T).

Molar heat capacity of liquids and solids is almost constant whereas it varies in gases.

Question 3

What is denoted by Cv and Cp?

Answer 3

Cp is molar heat capacity due to isobaric process and Cv is molar heat capacity due to isochoric process.

Question 4

What is the first law of thermodynamics ?

Answer 4

Q= ΔU + W.

It’s the law of conservation of energy.

Question 5

How to find work done using the first law of thermodynamics ?

Answer 5

W= p(Vf-Vi)=pΔV.
Is p is constant it means the process is adiabatic.
Work done can also be obtained by tea under p-V diagram with projection on V axis.

Question 6

In the first law of thermodynamics , what can you say about the sign of work done in various scenarios in p vs V graph?

Answer 6

W=+ve as volume increases.
W=-ve as volume decreased.
W=0 if volume is constant.
W=+ve as cyclic process is clockwise with p on y axis
W=-ve as cyclic process is anti-clockwise with p on y axis.

Question 7

Using the first law of thermodynamics, what is the formula of change is internal energy ΔU?

Answer 7

ΔU= n Cv ΔT. If either three terms are unknown then we can calculate ΔU by ΔU=Q-W.

Question 8

Using the first law of thermodynamics , what is the formula for heat exchange Q?

Answer 8

Q= n C ΔT. If all the three quantities are unknown then, calculate Q=ΔU+W.

Question 9

What can you say about isobaric process in term of x and slope ?

Answer 9

In isobaric process, x=0, therefore slope= 0.

Question 10

What can you say about isothermal process in terms of x and slope ?

Answer 10

In isothermal process , x=1 and therefore slope = p/v.

Question 11

What can you say about adiabatic process in terms of x and slope ?

Answer 11

x=γ and slope =-γ(p/V)