How Do We Calculate Entropy Change for an Ideal Gas?

[mooncrater]

Homework Statement

The question says:
In a process involving n moles of an ideal gas , what is the entropy change of the system ?

Homework Equations

ΔS=q_rev/T=(ΔU-w)/T
(I have used the chemistry's equation of 1st law of thermodynamics which has the -ve sign)

The Attempt at a Solution

The answer given is that:
nC_vln(T₂/T₁)+nRln(V₂/V₁).
I don't know how they are giving this answer. The second term seems to be originated from work done in isothermal conditions . But its not given that the process is an isothermal one. And the first term ...huh..I don't know where it came from. So what is the origin of this answer?

 

[Borek]

In a process

What process?

 

[mooncrater]

What process?

There is nothing else given in the question.