JEE MAIN - Chemistry Hindi (2019 - 8th April Morning Slot - No. 10)

निम्न में से कौन-सा समीकरण थर्मोडायनामिक्स के प्रथम सिद्धान्त को दिये गये प्रक्रमों के लिए, जिसमें आदर्श गैस है, सही रूप में प्रस्तुत नहीं करता है (मान लें कि अप्रसारण कार्य शून्य है ) :
रूद्धोष्म प्रक्रम : $$\Delta $$U= – w
चक्रीय प्रक्रम : q = –w
समायतनिक प्रक्रम : $$\Delta $$U= q
समतापी प्रक्रम : q = – w

Explanation

From 1st law of thermodynamics we know,

$$\Delta $$U = q + W

Option A :

In adiabatic process exchage of heat = 0

$$ \therefore $$ q = 0

$$ \therefore $$ From 1st law of thermodynaics, $$\Delta $$U = W

So option A is wrong.

Option B :

U is a state function. In cyclic process, initial state and final state both are same. So change in all the state function in cyclic process will be zero.

$$ \therefore $$ $$\Delta $$U = 0

$$ \therefore $$ From 1st law of thermodynaics,

q + W = 0 $$ \Rightarrow $$ q = -W

So option B is correct..

Option C :

In isochoric process volume (V) is constant. So dV = 0.

We know, W = $$ - \int {{P_{ex}}} dV$$

$$ \therefore $$ W = 0

$$ \therefore $$ From 1st law of thermodynaics,

$$\Delta $$U = q

So option C is correct.

Option D :

In isothermal process temerature (T) is constant. So dT = 0.

We know, $$\Delta $$U = nCvdT

$$ \therefore $$ $$\Delta $$U = 0

$$ \therefore $$ From 1st law of thermodynaics,

q + W = 0 $$ \Rightarrow $$ q = -W

So option D is correct.

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