All the naturally occurring processes, i.e., spontaneous proceed spontaneously in a direction that leads to:
decrease of free energy
increase of free energy
decrease of entropy
increase of enthalpy
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:
reversible process
cyclic process
isobaric process
spontaneous process
Warming ammonium chloride with sodium hydroxide in a test tube is an example of:
closed system
Isolated system
open system
None of these
Work done in the reversible adiabatic process is given by:
2.303 RT log (V2/V1)
nR (γ-1)(T2-T1)
2.303 RT log(V1/V2)
none of these
Change in enthalpy for reaction,
2H2O2(l)→ 2H2O(l) + O2(g)
If the heat of formation of H2O2(l) and H2O(l) are -188 and -286 kJ/mol respectively is -
-196 kJ/mol
+ 196 kJ/mol
+948 kJ/mol
-948 kJ/mol
One mole of a non-ideal gas undergoes a change of state (2.0 atm, 3.0 L, 95 K)→(4.0 atm, 5.0 L, 245 K) with a change in internal energy, ∆U = 30.0 L atm. The change in enthalpy (∆H) of the process in L atm is:
40.0
42.3
44.0
not defined, because pressure is not constant
At absolute zero, the entropy of a perfect crystal is zero. This is........... of thermodynamics.
The first law
Second law
Third law
None of the above
At constant pressure and temperature, the direction of any chemical reaction is one where the...... decrease.
Entropy
Enthalpy
Gibbs energy
The work done by a mass less piston in causing an expansion ∆V (at constant temperature), when the opposing pressure, P is variable, is given by:
W= -∫P∆V
W=0
W= -P∆V
Entropy decreases during:
crystallization of sucrose from solution
rusting of iron
melting of ice
vaporization of camphor
Entropy change of vaporization at constant pressure is given by:
∆S(v)=∆UvT
∆S(v)= ∆HvP
What is the entropy change for the reaction given below,
2H2 (g) + O2 (g) →2H2O(l)
at temperature 300 K? Standard entropies of H2 (g), O2(g) and H2O(l) are 126.6, 201.20 and 68.0 JK-1mol-1 respectively.
-318.4 JK-1mol-1 .
318.4 JK-1mol-1
31.84 JK-1mol-1
If S° for H2, Cl2 and HCl are 0.13, 0.22 and 0.19 kJ K-1mol-1 respectively. The total change in standard entropy for the reaction, H2 + Cl2 →2HCl is:
30 J K-1mol-1
40 J K-1mol-1
60 J K-1mol-1
20 J K-1mol-1
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:
T/(2)2/3
T + 2/(3x0.0821)
T
T - 3/(2x0.0821)
Which is not a spontaneous process?
Expansion of gas into the vacuum
Water flowing downhill
Heat flowing from a colder body to a hotter body
Evaporation of water from clothes during drying
The direct conversion of A to B is difficult and thus it is converted by path A→C→D→B. Given
∆SA→C=50 e.u; ∆SC→D=30 e.u; ∆SB→D=20 e.u.
Where e.u. is the entropy unit, then ∆SA→B is:
+60 e.u
+100 e.u
-60 e.u
-100 e.u
In a flask, colourless N2O4(g) is in equilibrium with brown coloured NO2(g). At equilibrium when the flask is heated to 100°C, the brown colour deepens and on cooling it becomes less coloured. Which statement is incorrect about this observation?
The ∆H for the reaction N2O4(g)⇌ 2NO2(g) is +ve
Paramagnetism increases on heating
The ∆H-∆U at 100°C is equal to 200 cal
Dimerisation is reduced on heating
Enthalpy of the reaction,
CH4(g) + 1/2 O2(g) →CH3OH (l), is negative. If the enthalpy of combustion of CH4 and CH3OH are x and y respectively, then which relation is correct?
x>y
x<y
x=y
x⩾y
In the reaction, ∆H and ∆S both are positive. The condition under which the reaction would not be spontaneous is -
∆H>T∆S
∆S=∆H/T
∆H=T∆S
All of the above
When an ideal gas is compressed adiabatically and reversibly, the final temperature is:
higher than the initial temperature
lower than the initial temperature
the same as the initial temperature
dependent on the rate of compression
1 liter-atmosphere is equal to:
101.3 J
24.206 cal
101.3 x 107 erg
The standard change is Gibbs energy for the reaction,
H2O⇄H+ + OH- at 25°C is:
100 kJ
-90 kJ
90 kJ
-100 kJ
The entropy change in the fusion of one mole of a solid melting at 27°C is -
(the latent heat of fusion is 2930 J mol-1)
9.77 JK-1mol-1
19.73 JK-1mol-1
2930 JK-1mol-1
108.5 JK-1mol-1
The maximum work done in expanding 16 g oxygen at 300 K and occupying a volume of 5 dm3 isothermally until the volume becomes 25 dm3 is:
2.01 x 103 J
+2.81 x 103 J
2.01 x 10-3 J
+2.01 x 10-6 J
1 mole of an ideal gas at 25°C is subjected to expand reversibly ten times of its initial volume. The change in entropy of expansion is:
19.15 JK-1mol-1
16.15 JK-1mol-1
22.15 JK-1mol-1
For the process
H2O(l) →H2O(g)
at T=100°C and 1 atmosphere pressure, the correct choice is:
∆Ssystem>0 and ∆Ssurrounding>0
∆Ssystem>0 and ∆Ssurrounding<0
∆Ssystem<0 and ∆Ssurrounding>0
∆Ssystem<0 and ∆Ssurrounding<0
During an adiabatic process:
pressure is maintained constant
gas is isothermally expanded
there is perfect heat insulation
the system changes heat with surroundings
Heat of combustion ∆H° for C(s), H2(g) and CH4(g) are -94, -68 and -213 kcal/mol. Then, ∆H° for
C(s) + 2H2(g) →CH4(g) is
-17 kcal/mol
-111 kcal/mol
-170 kcal/mol
-85 kcal/mol
If 50 calorie are added to a system and system does work of 30 calorie on surroundings, the change in internal energy of system is:
20 cal
50 cal
40 cal
30 cal
For the process:
H2O(l)[1 bar, 373 K] ⇌H2O(g)[1 bar, 373 K] the correct set of thermodynamic parameters are:
∆G=0; ∆S=+ve
∆G=0; ∆S=-ve
∆G=+ve; ∆S=0
∆G=-ve; ∆S=+ve
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