Question

Classify the following processes as reversible or irreversible : 

(i) Dissolution of sodium chloride 

(ii) Evaporation of water at 373 K and 1 atm. pressure 

(iii) Mixing of two gases by diffusion 

(iv) Melting of ice without rise in temperature 

(b) When an ideal gas expands is vacuum, there is neither absorption nor revolutions of what? why?

Answer 1

(a)(i) Irreversible, 

(ii) Irreversible, 

(iii) Irreversible, 

(iv) Reversible 

(b) It is because no work is done, 

i.e., w = 0 w = -pext × ΔV = 0 × ΔV = 0 

In ΔU = q + w 

q = 0 because gas chamber is insulated ΔU = 0 + 0 = 0