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Quiz 4
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Q.1
Heat of combustion of acetylene is ... [ EAMCET 1994]
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a) +228 kJ
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b) -228 kJ
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c) +100 kJ
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d) -100 kJ
Explanation
Answer: (b)
Q.2
The heat of neutralization of aqueous hydrochloric acid by NaOH is x kcal/mole of HCl. Calculate the heat of neutralization per mole of aqueous acetic acid .. [ ISM Dhanbad 1994]
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a) 0.5x kcal
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b) x kcal
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c) 2x kcal
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d) can not be calculated from the iven data
Explanation
Heat of dissociation of acetic acid is not known, hence heat of neutralization can not be calculated Answer: (d)
Q.3
Which of the following statement is true? The entropy of the universe.. [ MP PMT 1993]
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a) Increase and tends towards maximum value
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b) decreases and tends to zero
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c) remains constant
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d) decreases and increases with a periodic rate.
Explanation
Answer: (a)
Q.4
Gibb's free energy G, enthalpy H and entropy S are related to one another by ... [ BHU 1994]
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a) G=H + TS
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b) G=H - TS
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c) G - TS=H
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d) S=H - G
Explanation
Answer: (b)
Q.5
ΔS° will be highest for reaction ... [ AIIMS 1994]
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a) Ca(s) + ½O2(g) → CaO(s)
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b) CaCO3(s) → CaO(s) + CO2(g)
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c) C + O2 → CO2(g)
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d) N2(g) + O2(g) → 2NO(g)
Explanation
in option (b) solid changes to gas Answer: (b)
Q.6
Heat of neutralization of strong acid against strong base is constant and is equal to.. [ MP PMT 1999]
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a) 13.7 kcal
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b) 57 kJ
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c) 5.7 ×104 J
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d) All of the above
Explanation
Answer: (d)
Q.7
The total entropy for a system and its surrounding increases, if the process is ...[ MP PMT]
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a) reversible
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b) irreversible
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c) exothermic
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d) endothermic
Explanation
Entropy is the loss of energy available to do work. Another form of the second law of thermodynamics states that the total entropy of a system either increases or remains constant; it never decreases. Entropy is zero in a reversible process; it increases in an irreversible process. Answer: (b)
Q.8
A chemical reaction will be spontaneous if it is accompanied by a decrease of ... [CBSE PMT 1994]
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a) entropy of the system
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b) enthalpy of the system
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c) internal energy of the system
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d) free energy of the system
Explanation
Answer: (d)
Q.9
Consider the following reaction occurring in an automobile2C8H18(g) + 25O2(g) → 16CO2 + 18H2O (g)the sign of ΔH, ΔS and ΔG would be.. .. [ CBSE PMT 1994]
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a) +, - , +
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b) -, +, -
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c) -, +, +
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d) +, +, -
Explanation
Answer: (b)
Q.10
Which of the following is true for the reactionH2O(l) ⇌ H2O (g) at 100°C and 1atmosphere? [ KCET 1991]
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a) ΔS=0
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b) ΔH=0
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c) ΔH=ΔE
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d) ΔH=T ΔS
Explanation
At equilibrium ΔG=0 Hence 0=ΔH - TΔSAnswer: (d)
Q.11
For a system in equilibrium, ΔG=0, under conditions of constant... [ KCET 1991]
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a) temperature and pressure
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b) temperature and volume
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c) energy and volume
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d) pressure and volume
Explanation
Answer: (a)
Q.12
Enthalpy for the reaction C + O2→ CO2 is ... [ DPMT 1987]
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a) positive
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b) negative
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c) zero
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d) none
Explanation
reaction is exothermic Answer: (b)
Q.13
At a given temperature, the energy of activation of two reactions is same if ...[ IIT 1993]
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a) the specific rate constant for the two reactions is same
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b) the temperature coefficient for the specific rate constant for the two reactions is same
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c) ΔH from the two reactions is the same but not zero
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d) ΔH for the two reaction is zero
Explanation
From equation At a given temperature if activation energy (Ea are same then k sameAnswer: (a)
Q.14
Enthalpy of a compound is equal to its... [ CMC Vellore 1991]
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a) heat of combustion
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b) Heat of formation
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c) heat of reaction
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d) heat of solution
Explanation
Answer: (b)
Q.15
Identify the state function among the following ... [ IIT 1993]
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a) q
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b) q-w
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c) q/w
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d) q+w
Explanation
q+w=ΔE is a state function Answer: (d)
Q.16
When 0.2 g of butanol-1 was burnt in a suitable apparatus, the heat evolved was sufficient to raise the temperature of 200g water by 5°C. The heat of combustion of butanol-1 in kcal/mole will be ( mol mass of butanol-1=74)
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b) 74
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c) 37
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a) 14.8
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d) 370
Explanation
Heat evolved=absorbed by water to increase temperatureHeat evolved=m×S×ΔT Heat evolved from 0.2g=200×1×5=1 kcal∴ heat evolved from 1 mole i.e 74g=370 kcalAnswer: (d)
Q.17
During isothermal expansion of an ideal gas, its... [ CBSE PMT 1994]
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a) internal energy increases
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b) enthalpy decreases
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c) enthalpy remains unaffected
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d) enthalpy reduces to zero
Explanation
During isothermal expansion ΔT=0, ΔE=0 Also Δng=0From equationΔH=ΔE + ΔnRTΔH=0 + 0=0Answer: (c)
Q.18
A particular reaction has a negative value for free energy change. Then at ordinary temperature .. [ Pb. CET 1991]
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a) it has a large -ve value for entropy change
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b) it has a large +ve value for enthalpy change
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c) it has a large +ve value for enthalpy change
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d) it has a +ve value for entropy change and a -ve value for the enthalpy change
Explanation
From equation ΔG=ΔH - TΔS Answer: (d)
Q.19
For an endothermic reaction where ΔH represents the enthalpy of the reaction in kJ/mol, the minimum value for the energy of activation will be ... [ IIT 1992]
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a) less than ΔH
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b) zero
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c) more than ΔH
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d) equal to ΔH
Explanation
Energy of activation is higher than ΔH Answer: (c)
Q.20
The heat of combustion of benzene at 27°C found by bomb calorimeter i.e. for the reactionC6H6(l) + 7.5 O2(g) → 6CO2(g) + 3H2O(l)is 780 kcal/mol. The heat evolved on burning 39g of benzene in an open vessel will be .. [ Manipal PMT 2001]
0%
a) 390 kcal
0%
b) 780.9 kcal
0%
c) 390.45 kcal
0%
d) 780 kcal
Explanation
given : heat of combustion=ΔE=-780 kcal Δng=6 - 7.5=-1.5 ΔH=ΔE + ΔngRTΔH=-780 - 1.5 × 2×10-3×300ΔH=-780.9 kcal/molThis is the heat evolved from 1 mole of benzene i.e. 78g∴ From 39g, heat evolved=780.9 / 2=390.45 kcalAnswer: (c)
Q.21
Which one of the following bonds has the highest average bond energy (kcal/mol)? [ CPMT 1992]
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a) S=O
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b) C=C
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c) C Ξ N
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d) N Ξ N
Explanation
Answer: (d)
Q.22
Foe the spontaneity of a reaction which statement is true? [ KCET 1988]
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a) ΔG=+ve ; ΔH=+ve
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b) ΔH=+ve; ΔS=-ve
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c) ΔG=-ve; ΔS=-ve
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d) ΔH=-ve; ΔS=+ve
Explanation
Answer: (d)
Q.23
The amount of heat measured for a reaction in bomb calorimeter is ... [ AIIMS 1991]
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a) ΔG
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b) ΔH
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c) ΔE
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d) PΔV
Explanation
Answer: (c)
Q.24
One mole of methanol, when burnt in oxygen, gives out 723kJ/mol heat. If one mole oxygen is used, what will be the amount of heat evolved? [ DCE 1994]
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a) 723 kJ
0%
b) 964 kJ
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c) 482 kJ
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d) 241 kJ
Explanation
CH3OH + (3/2) O2 → CO2 + 2H2O With 1 mole of O2, ΔH=(2/3)×723=482 kJAnswer: (c)
Q.25
A well stoppered thermos flask contains some ice cubes. This is an examples of a ... [ AIIMS 1974]
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a) closed system
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b) open system
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c) isolated system
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d) non-thermodynamics system
Explanation
Answer: (c)
Q.26
In which of the following neutralization reaction, the heat of neutralization will be highest? [ MP PMT 1991]
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a) NH4OH and H2SO4
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b) HCl and NaOH
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c) CH3COOH and KOH
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d) CH3COOH and NH4OH
Explanation
In option "b" both acid and base are strong Answer: (b)
Q.27
A system changes its state from A to B. The resulting change of entropy will be a definite quantity ... [ Pb CET 1991]
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a) When the change is reversible one
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b) When change is irreversible one
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c) When the change is an isothermal one
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d) always irrespective of the manner in which the change is brought about
Explanation
This is because entropy is state function Answer: (d)
Q.28
For the reactionN2 + 3H2 ⇌ 2NH3, ΔH=? .. [ CBSE PMT 1991]
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a) ΔE + 2RT
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b) ΔE - 2RT
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c) ΔE + RT
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d) ΔE - RT
Explanation
Δng=2 -4=-2 ΔH=ΔE + ΔngRTΔH=ΔE - 2RTAnswer: (b)
Q.29
An exothermic reaction is one in which the reacting substances.. [ CPMT 1974]
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a) Have more energy than the product
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b) Have less energy than the products
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c) Have the same energy as the products
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d) are at a higher temperature than the products.
Explanation
Answer: (a)
Q.30
The heat absorbed in a reaction at constant temperature and volume is equal to ..[ Pb. CET 1991]
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a) ΔU of the reaction
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b) ΔHof the reaction
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c) -ΔU of the reaction
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d) -ΔH of the reaction
Explanation
heat absorbed at constant volume, no work, from first law of thermodynamics qv=ΔUAnswer: (a)
0 h : 0 m : 1 s
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