Sublimation temperature of dry ice (solid CO2) is __________ °C.
-273
0
-78
5
Correct Answer :
C. -78
Related Questions
Equation which relates pressure, volume and temperature of a gas is called the
Equation of state
Gibbs Duhem equation
Ideal gas equation
None of these
The absolute entropy for all crystalline substances at absolute zero temperature is
Zero
Negative
More than zero
Indeterminate
A refrigerator works on the principle of __________ law of thermodynamics.
Zeroth
First
Second
Third
For spontaneous changes in an isolated system (S = entropy)
ds = 0
ds <0
ds > 0
ds = Constant
Second law of thermodynamics is concerned with the
Amount of energy transferred
Direction of energy transfer
Irreversible processes only
Non-cyclic processes only
Pick out the wrong statement.
Minimum number of degree of freedom of a system is zero
Degree of freedom of a system containing a gaseous mixture of helium, carbon dioxide and hydrogen is 4
For a two phase system in equilibrium made up of four non-reacting chemical species, the number of degrees of freedom is 4
Enthalpy and internal energy change is zero during phase change processes like melting, vaporisation and sublimation
As the entropy of the universe is increasing, day by day, the work producing capacity of a heat engine is
Not changed
Decreasing
Increasing
Data sufficient, can't be predicted
Adiabatic compression of a saturated water vapour makes it
Supersaturated
Superheated
Both (A) and (B)
Neither (A) nor (B)
As the temperature is lowered towards the absolute zero, the value of the quantity (∂ΔF/∂T) approaches
Zero
Unity
Infinity
None of these
A refrigeration cycle is the same as a __________ cycle,
Turbine
Heat engine
Reversed heat engine
None of these
High pressure steam is expanded adiabatically and reversibly through a well insulated turbine, which produces some shaft work. If the enthalpy change and entropy change across the turbine are represented by ΔH and ΔS respectively for this process:
Δ H = 0 and ΔS = 0
Δ H ≠ 0 and ΔS = 0
Δ H ≠ 0 and ΔS ≠ 0
Δ H = 0 and ΔS ≠ 0
For multi-component multiple phases to be in equilibrium at the same pressure and temperature, the __________ of each component must be same in all phases.
Chemical potential
Fugacity
Both (A) and (B)
Neither (A) nor (B)
Filling of gas from a high pressure cylinder into small bottles is an example of a/an __________ process.
Equilibrium
Adiabatic
Steady
Unsteady
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
In which of the following reaction equilibrium, the value of equilibrium constant Kp will be more than is Kc?
2HI H2 + I2
N2O4 2NO2
2SO2 + O2 2SO3
None of these
During Joule-Thomson expansion of gases
Enthalpy remains constant
Entropy remains constant
Temperature remains constant
None of these
For a constant pressure reversible process, the enthalpy change (ΔH) of the system is
Cv.dT
Cp.dT
∫ Cp.dT
∫ Cv.dT
Pick out the correct statement.
Entropy and enthalpy are path functions
In a closed system, the energy can be exchanged with the surrounding, while matter cannot be exchanged
All the natural processes are reversible in nature
Work is a state function
Which of the following decreases with increase in pressure?
Melting point of ice
Melting point of wax
Boiling point of liquids
None of these
Which of the following is not affected by temperature changes?
Fugacity
Activity co-efficient
Free energy
None of these
Fundamental principle of refrigeration is based on the __________ law of thermodynamics.
Zeroth
First
Second
Third
Reduced pressure of a gas is the ratio of its
Pressure to critical pressure
Critical pressure to pressure
Pressure to pseudocritical pressure
Pseudocritical pressure to pressure
When pressure is applied on the system, ice ↔ water, then
Equilibrium cannot be established
More ice will be formed
More water will be formed
Evaporation of water will take place
The internal energy of an ideal gas does not change in a reversible __________ process.
Isothermal
Adiabatic
Isobaric
Isometric
At the critical point of a substance
The surface tension vanishes
Liquid and vapour have the same density
There is no distinction between liquid and vapour phases
All (A), (B) and (C)
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
Which of the following is not correct for a reversible adiabatic process?
TVγ-1 = constant
p1-γ.TY = constant
PVγ = constant
None of these
Trouton's ratio is given by (where λb, = molal heat of vaporisation of a substance at its normal boiling point, kcal/kmol Tb = normal boiling point, °K)
λb/Tb
Tb/λb
√(λb/Tb)
√(Tb/λb)
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
The molar excess Gibbs free energy, gE, for a binary liquid mixture at T and P is given by, (gE/RT) = A . x1. x2, where A is a constant. The corresponding equation for ln y1, where y1 is the activity co-efficient of component 1, is
A . x22
Ax1
Ax2
Ax12