Chemistry MCQs for NEET — Practice Questions with Answers

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Change in entropy is negative for:

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Explanation

(d) The gaseous phase have more entropy and thus, S is +ve in (a) and (b). Also decrease in pressure increase disorder and thus, S is +ve in (c). In (d) the disorder decreases in liquid state due to the decrease in temperature. Thus, S= -ve

The mathematical form of the first law of thermodynamics when heat (q) is supplied and W is work done by the system (+ve) is:

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Explanation

(b) If work done by the system is positive, then q=U+W. However, new terminology has revealed that work done by the system is negative and work done on the system is positive. Thus, according to this, q=E-W.

Which statements are correct?

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Explanation

(d) These all are facts.

S° will be highest for the reaction:

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Explanation

(b) Gaseous product is formed; more positive is n, more is entropy.

One mole of ice is converted into water at 273 K. The entropies of H2O(s) and H2O(l) are 38.20 and 60.01 J mol-1K-1 respectively. The enthalpy change for the conversion is:

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Explanation

(b) G=H-TS; at equilibrium,G=0,       ...H=TS

       or H = 273 x (60.01-38.20) = 5954.13 J mol-1

A gaseous system changes from state A(P1, V1, T1) to B(P2,V2,T2), B to C(P3, V3, T3) and finally from C to A. The whole process may be called:

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Explanation

(b) The system returns to its original state, i.e, cyclic process.

When one mole of monoatomic ideal gas at TK undergoes reversible adiabatic change under a constant external pressure of 1 atm changes volume from 1 litre to 2 litre. The final temperature in kelvin would be:

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Explanation

(a) TV r-1 =K

      T1V1r-1= T2V2r-1

      T1V12/3= T2V22/3                       (r=5/3 for monoatomic)

         T1/T2 = (V2/V3)2/3   = (1/2)2/3 

           ... T2 = T/(2)2/3

Which is not a spontaneous process?

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Explanation

(c) Heat cannot be itself pass from colder to hotter body.

All the naturally occurring processes, i.e., spontaneous proceed spontaneously in a direction which leads to:

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Explanation

(a) For a spontaneous process G=-ve or <0.

In which case entropy decreases?

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Explanation

3. In stretching of rubber band, entropy decreases because molecules are arranged in ordered form.

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