Chemical Engineering Thermodynamics - Study Mode
[#136] C p - C v = R is valid for __________ gases.
Correct Answer
(A) Ideal
Explanation
Solution: $${C_P} - {C_V} = R,$$ xa0 xa0is valid for ideal gas and we can prove this by using $$T-dS$$ xa0equations.
[#137] The change in Gibbs freee energy for vaporisation of a pure substance is
Correct Answer
(C) Zero
Explanation
Solution: Since, the gibbs free energy for vaporization of a pure substance is $$dG=VdP-SdT$$ xa0 xa0since during phase change the temperature and pressure remains constant the gibbs free energy remains constant.
[#138] The chemical potential for a pure substance is __________ its partial molal free energy.
Correct Answer
(C) Equal to
Explanation
Solution: The chemical potential is nothing but the partial molar gibbs free energy. $${mu _i} = left( {frac{{partial nG}}{{partial {n_i}}}}
ight)d{n_i}$$
[#139] For a given substance at a specified temperature, activity is __________ to fugacity.
Correct Answer
(A) Directly proportional
Explanation
Solution: For a given substance the activity is defined as ratio of fugacity at conditions of interest to fugacity at standard state, the standard state can be anything where the fugacity is known know, if you keep the standard state same and change the conditions of interest where you want to find out the fugacity then we can say that the activity becomes directly proportional to fugacity. $$ Rightarrow {a_i} = frac{{{f_i}}}{{f_i^o}}$$
[#140] The unit of fugacity is the same as that of the
Correct Answer
(A) Pressure
Explanation
Solution: The fugacity is nothing but effective pressure and hence unit of fugacity is same as pressure.