A change in state involving a decrease in entropy can be spontaneous, only if
It is exothermic
It is isenthalpic
It takes place isothermally
It takes place at constant volume
Correct Answer :
A. It is exothermic
Related Questions
The partial molar enthalpy of a component in an ideal binary gas mixture of composition Z, at a temperature T and pressure P, is a function only of
T
T and P
T, P and Z
T and Z
On a P-V diagram of an ideal gas, suppose a reversible adiabatic line intersects a reversible isothermal line at point A. Then at a point A, the slope of the reversible adiabatic line (∂P/∂V)s and the slope of the reversible isothermal line (∂P/ ∂V)T are related as (where, y = Cp/Cv)
(∂P/∂V)S = (∂P/∂V)T
(∂P/∂V)S = [(∂P/∂V)T]Y
(∂P/∂V)S = y(∂P/∂V)T
(∂P/∂V)S = 1/y(∂P/∂V)T
Free energy change of mixing two liquid substances is a function of the
Concentration of the constituents only
Quantities of the constituents only
Temperature only
All (A), (B) and (C)
For a multi-component system, the term chemical potential is equivalent to the
Molal concentration difference
Molar free energy
Partial molar free energy
Molar free energy change
Ideal gas law is applicable at
Low T, low P
High T, high P
Low T, high P
High T, low P
A reasonably general expression for vapourliquid phase equilibrium at low to moderate pressure is φi yi P = Yi xifi° where, Φ is a vapor fugacity component, Yi is the liquid activity co-efficient and fi° is the fugacity of the pure component i. the Ki value (Yi = Ki xi) is therefore, in general a function of
Temperature only
Temperature and pressure only
Temperature, pressure and liquid composition xi only
Temperature, pressure, liquid composition xi and vapour composition yi
For an ideal gas, the activity co-efficient is
Directly proportional to pressure
Inversely proportional to pressure
Unity at all pressures
None of these
The theoretical minimum work required to separate one mole of a liquid mixture at 1 atm, containing 50 mole % each of n- heptane and noctane into pure compounds each at 1 atm is
-2 RT ln 0.5
-RT ln 0.5
0.5 RT
2 RT
Gibbs free energy of a pure fluid approaches __________ as the pressure tends to zero at constant temperature.
Infinity
Minus infinity
Zero
None of these
Helmholtz free energy (A) is defined as
A = H - TS
A = E - TS
A = H + TS
None of these
What happens in a reversible adiabatic expansion process?
Heating takes place
Cooling takes place
Pressure is constant
Temperature is constant
The expression, nCv(T2 - T1), is for the __________ of an ideal gas.
Work done under adiabatic condition
Co-efficient of thermal expansion
Compressibility
None of these
Maxwell's relation corresponding to the identity, dH = dS = Vdp + Σμi dni is
(∂T/∂V)S, ni = -(∂P/∂S)V, ni
(∂S/∂P)T, ni = (∂V/∂T)P, ni
(∂S/∂V)T, ni = (∂P/∂T)V, ni
(∂T/∂P)S, ni = (∂V/∂S)P, ni
Specific __________ does not change during a phase change (e.g. sublimation, melting, vaporisation etc.).
Entropy
Internal energy
Enthalpy
Gibbs free energy
For an isothermal process, the internal energy of a gas
Increases
Decreases
Remains unchanged
Data insufficient, can't be predicted
Enthalpy 'H' is defined as
H = E - PV
H = F - TS
H - E = PV
None of these
Isotherm on an enthalpy-concentration diagram, for an ideal solution will be a
Straight line
Sine curve
Parabola
Hyperbola
When a gas in a vessel expands, its internal energy decreases. The process involved is
Reversible
Irreversible
Isothermal
Adiabatic
The expression, nRT ln(P1/P2), is for the __________of an ideal gas.
Compressibility
Work done under adiabatic condition
Work done under isothermal condition
Co-efficient of thermal expansion
Molar heat capacity of water in equilibrium with ice at constant pressure is __________ Kcal/kg mole. °K
0
∞
50
100
Gibbs-Duhem equation
States that n1dμ1 + n2dμ2 + ....njdμj = 0, for a system of definite composition at constant temperature and pressure
Applies only to binary systems
Finds no application in gas-liquid equilibria involved in distillation
None of these
The necessary and sufficient condition for equilibrium between two phases is
The concentration of each component should be same in the two phases
The temperature of each phase should be same
The pressure should be same in the two phases
The chemical potential of each component should be same in the two phases
If an ideal solution is formed by mixing two pure liquids in any proportion, then the __________ of mixing is zero
Enthalpy
Volume
Both 'a' & 'b'
Neither 'a' nor 'b'
Which one is true for a throttling process?
A gas may have more than one inversion temperatures
The inversion temperature is different for different gases
The inversion temperature is same for all gases
The inversion temperature is the temperature at which Joule-Thomson co-efficient is infinity
Translational kinetic energy of molecules of an ideal gas is proportional to (where, T = absolute temperature of the gas)
T
√T
T2
1/√T
The total change in the enthalpy of a system is independent of the
Number of intermediate chemical reactions involved
Pressure and temperature
State of combination and aggregation in the beginning and at the end of the reaction
None of these
The minimum number of phases that can exist in a system is
0
1
2
3
On opening the door of an operating refrigerator kept in a closed room, the temperature of the room will
Increase
Decrease
Remain same
Increase in summer and will decrease in winter
What is the number of degrees of freedom for liquid water in equilibrium with a mixture of nitrogen and water vapor?
2
0
3
1
Isentropic process means a constant __________ process.
Enthalpy
Pressure
Entropy
None of these