MUNISH KAKAR's INSTITUTE OF CHEMISTRY
APPLICATION OF FIRST LAW & ENTHALPY CHANGE WS #1
Q1.
The work done, when ‘x’ moles of an ideal gas expand freely into the vacuum is:
(a) positive
Q2.
Q3.
(b) zero
(c) negative
(d) infinite
Energy equivalent to one erg, one joule and one calorie is in the order:
(a) 1 erg > 1 joule > 1 calorie
(b) 1 erg > 1 calorie > 1 joule
(c) 1 calorie > 1 joule > 1 erg
(d) None of these
Which among the following is correct regarding an closed system ?
(a) Involves exchange in mass as well as heat
(b) Involves exchange in mass but not heat
(c) Involves exchange in heat but no exchange in mass
(d) neither exchange in mass nor exchange in heat
Q4.
Which among the following is correct regarding an isolated system ?
(a) During expansion temperature increases
(b) During compression temperature increases
(c) Involves no exchange in mass as well as heat
(d) both b and c
Heat absorbed by a system in going through a cyclic process shown in figure is:
(a) 107 J
(b) 106 J
(c) 102 J
(d) 104 J
30
V(in L)
Q5.
10
30
10
P(in KPs)
Q6.
An ideal gas expands in volume from 1  10-3 m3 to 1  10-2 m3 at 300 K against a
constant pressure of 1  105 Nm-2. The work done is:
(a) 270 kJ
Q7.
(b) – 900 kJ
(c) – 900 J
(d) 900 kJ
One mole of an ideal gas at 300 K is expanded isothermally from an initial volume of 1
litre to 10 litre. The change in internal energy for this process is:(R = 2 cal mol -1 K-1)
(a) 163.7 cal
Q8.
(b) 859.2 cal
(c) 1381.1 cal
(d) zero
The ‘q’ value and work done in the isothermal reversible expansion of one mole of an ideal
gas from an initial pressure of 1.0 bar to final pressure of 0.1 bar at a constant
temperature of 273 K are:
(a) 5.22 kJ, -5.22 kJ
(b) -5.22 kJ, 5.22 kJ
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(c) 5.22 kJ, 5.22 kJ
Q9.
(d) -5.22 kJ, -5.22 kJ
A system is changed from state A to state B by one path and from B to A another path. If
E1 and E2 are the corresponding changes in internal energy, then:
(a) E1 + E2 = -ve
(b) E1 + E2 = +ve
(c) E1 + E2 = 0
(d) none of these
Q10. The volume of a gas decreases from 500 cc to 300 cc when a sample of gas is compressed
by an average pressure of 0.6 atm. During this process, 10 J of heat is liberated. The
change in internal energy is:
(a) – 2.16 J
(b) 12.56 J
(c) 2.16 J
(d) 101.3 J
Q11. For the reaction: C3H8(g) + 5O2(g)  3CO2(g) + 4H2O(l) , H - E is:
(a) –3RT
(b) +RT
(c) -2RT
(d) +3RT
Q12. For an adiabatic process, which of the following relations is correct?
(a) ∆E = 0
(b) P ∆V = 0
(c) q = 0
(d) q = + w
Q13. Which one is true from the following for isobaric process ?
(a) ∆P = 0
(b) ∆q = 0
(c) ∆H = 0
(d) ∆E = 0
Q14. A process, in which pressure remains constant, is called:
(a) isochoric process (b) isothermal process (c) adiabatic process (d) isobaric process
Q15. For a cyclic process, the condition is:
(a) ∆E = 0
(b) ∆H = 0
(c) ∆E > 0 and ∆H > 0 (d) both ∆E = 0 and ∆H = 0
Q16. Which one of the following is a state property?
(a) Heat
(b) Work
(c) Internal energy (d) Potential energy
Q17. For the reaction of one mole zinc dust with one mole sulphuric acid in a bomb
calorimeter, ∆U and w correspond to:
(a) ∆U < 0, w = 0
(b) ∆U < 0, w < 0
(c) ∆U > 0, w = 0
(d) ∆U > 0, w > 0
Q18. A system is provided with 50 joules of heat and the work done on the system is 10 joules.
What is the change in internal energy of the system in joules?
(a) 60
(b) 40
(c) 50
(d) 10
Q19. The work done in ergs for a reversible expansion of one mole of an ideal gas from a volume
of 10 litre to 20 litre at 25°C is:
(a) 2.303 × 8.31 × 107 × 298 log 2
(c) 2.303 × 0.0821 × 298 log 0.5
(b) 2.303 × 0.0821 × 298 log 2
(d) None of these
Q20. When an ideal gas is compressed adiabatically and reversibly, the final temperature is:
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(a) higher than the initial temperature
(b) lower than the initial temperature
(c) the same as initial temperature
(d) dependent upon the rate of compression
Q21. The work done when 1 mol of an ideal gas is compressed reversibly from 1 bar to 4 bar at
a constant temperature of 300 K is ;
(a) 3.45 kJ
(b) -8.02 kJ
(c) 18.02 kJ
(d) -14.01 kJ
Q22. The difference between heats of reaction at constant pressure and constant volume for the
reaction,2C6H6(l) + 15O2(g) → 12CO2(g) + 6H2O(l) at 25°C in kJ is:
(a) +7.43
(b) +3.72
(c) -7.43
Q23. According to the equation,C6H6(l) +
(d) -3.72
15
O2(g) → 6CO2(g) + 3H2O(l);
2
∆H = -3264.4 kJ mol-1
the energy evolved when 7.8 g benzene is burnt in air will be:
(a) 163.22 kJ
(b) 32.64 kJ
Q24. ∆H and ∆E for the reaction, S(s) +
(a) ∆H = ∆E – 0.5 RT
Q25. S +
(c) 3.264 kJ
(d) 326.4 kJ
3
O2(g) → SO3(g) are related as:
2
(b) ∆H = ∆E – 1.5RT (c) ∆H = ∆E + RT
(d) ∆H = ∆E + 1.5 RT
3
O2 → SO3 + 2x kcal;SO2 + ½ O2 → SO3 + y kcal . The heat of formation of SO2 is:
2
(a) y – 2x
(b) 2x + y
(c) x + y
(d) 2x/y
Q26. Given,
NH3(g) + 3Cl2(g)  NCl3(g) + 3HCl(g);
-∆H1
N2(g) + 3H2(g)  2NH3(g);
-∆H2
H2(g) + Cl2(g)  2HCl(g);
-∆H3
The heat of formation of NCl3(g) in terms of ∆H1, ∆H2 and ∆H3 is:
(a) ∆Hf = -∆H1 + ½ ∆H2 - ∆H3
g
(c) ∆Hf = ∆H1 - ½ ∆H2 -
3
∆H3
2
(b) ∆Hf = ∆H1 + ½ ∆H2 -
3
∆H3
2
(d) none of the above
Q27. A gas occupies 2 litre at STP. It is provided 300 joule heat so that its volume becomes 2.5
litre at 1 atm. Calculate change in its internal energy.
+ 249.35 J
Q28. Two litre of N2 at 0oC and 5 atm pressure are expanded isothermally against a constant
external pressure of 1 atm unit the pressure of gas reaches 1 atm. Assuming gas to be
ideal, calculate work of expansion.
 8 L atm
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Q29. 2.8 g of N2 gas at 300 K and 20 atm was allowed to expand isothermally against a
constant external pressure of 1 atm. Calculate U, q and W for the gas.
Ans : U = 0 , q = + 2.34 L atm , w =  2.34 L atm
Q30. 10 g of argon gas is compressed isothermally and reversibly at a temperature of 27 oC from
10 L to 5 L. Calculate q. W, and U for this process R = 2.0 cal K-1 mol-1, log10 2 = 0.30.
Atomic wt. of Ar = 40.
Ans : q =  104 cal , w = + 104 cal
Q31. What happens to the internal energy of Isolated system if:
(a) work is done on the system,
(b) work is done by the system?
(A) Internal energy increases
(b) Internal energy decreases
Q32. A cooking gas cylinder is assumed to contain 11.2 kg isobutene having heat of
combustion -2658 kJ mol-1. If a family needs 15  103 kJ energy per day for cooking how
long a cylinder can last. Also if 30% heat is lost due to incomplete combustion, then how
long would it take to last.
Ans : 10.6 days
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