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Quiz 7
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Q.1
Consider the following reaction occuring in an automobile 2C8H18(g) +25O2(g) → 16CO2(g) + 18H2O(g) The sign of ΔH , ΔS and ΔG would be [ AIPMT 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.2
During isothermal expansion of an ideal gas its... [ AIPMT 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
Answer: (c)
Q.3
For the reaction N2 + 3H2 ⇒ 2NH3, ΔH = ? [ AIPMT 1991]
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a) ΔE + 2RT
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b) ΔE - 2RT
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c) ΔH = RT
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d) ΔE - RT
Explanation
Answer: (b)
Q.4
If enthapies of formation of C2H4(g), CO2(g) and H2O(l) at 25° and 1atm pressure are 52, -394, and -286kJ/mol, the enthalpy of combusion pf ethene is equl to [AIPMT 1995]
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a) -141.2 kJ/mol
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b) -1412 kJ/mol
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c) +14.2 kJ/mol
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d) +1412 kJ/mol
Explanation
Answer: (b)
Q.5
Given that C(s) + O2(g) → CO2(g), ΔH&dge = -x kJ 2CO(g) + O2 → 2CO2(g), ΔH&dge = -ykJ The enthalpy of formation of carbon monoxide will be .. [ AIPMT 1997]
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a) y - 2x
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b) 2x-y
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c) (y-2x)/2
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d) (2x-y)/2
Explanation
Answer: (c)
Q.6
Enthalpy of the reaction, CH4 + ½O2 → CH3OH is negative. if enthalpy of combustion of CH4 and CH3OH are 'x' and 'y' respectively, then which relation is correct? [ AIPMT 2001]
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a) x > y
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b) x < y
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c) x = y
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d) x ≥ y
Explanation
Answer: (c)
Q.7
For which one of the following equations ΔH°r equal to ΔH°f for the product? [ AIPMT 2003]
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a) Xe(g) + 2F2(g) → XeF4(g)
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b) 2CO(g) + O2(g) → 2CO2(g)
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c) N2(g) + O3(g) → N2O3(g)
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d) CH4(g) + 2Cl2 → CH2Cl2(l) + 2HCl(g)
Explanation
Answer: (a)
Q.8
If the bond energies of H-H, Br-Br and H-Br are 433, 192, and 364 kJmol- respectively, then ΔH° for the reaction H2(g) + Br2(g) → 2HBr(g) is .... [ AIPMT 2004]
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a) -261 kJ
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b) +103kJ
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c) +261kJ
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d) -103 kJ
Explanation
Answer: (a)
Q.9
A reaction occurs spontaneously if ... [ AIPMT 2005]
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a) TΔS < ΔH and both ΔH and ΔS are +ve
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b) TΔS > ΔH and both ΔH and ΔS are +ve
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c) TΔS = ΔH and both ΔH and ΔS are +ve
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d) TΔS > ΔH and ΔH is +ve and ΔS are -ve
Explanation
Answer: (b)
Q.10
Which of the following pairs of a chemical reaction is certain to result in a spontaneous reaction? [ AIPMT 2005]
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a) Exothermic and decreasing disorder
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b) Endothermic and increasing disorder
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c) Exothermic and increasing disorder
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d) Endothermic and decreasing disorder
Explanation
Answer: (c)
Q.11
Standard enthalpy of vaporization ΔvapH° for water at 100°C is 40.66 kJ mole-The internal energy of vaporisation of water at 100&dgeC (inkJ mol-1) is (assume water vapour to behace like an ideal gas)[ AIPMT 2012]
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a) +37.56
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b) -43.76
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c) +43.76
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d) +40.66
Explanation
Answer: (a)
Q.12
The enthalpy of fusion of water is 1.435 kcal/mol. the molar entropy change for the melting of ice at 0°C is [ AIPMT 2012]
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a) 10.52 cal/mol K
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b) 21.04 cal/mol K
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c) 5.260 cal/mol K
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d) 0.526 cal/mol k
Explanation
Answer: (c)
Q.13
Given C + 2S → CS2 , ΔHfo=+ 117.0 kJ/molC+ O2 → CO2 , ΔHfo=- 393.0 kJ/molS+ O2 → SO2 , ΔHfo=- 287.0 kJ/mol The heat of combustion of CS2 + 3O2 → CO2 + 2SO2 is ... [ KCET 1994]
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a) - 807 kJ/mol
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b) -1084 kJ/mol
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c) +1104 kJ/mol
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d) +807 kJ/mol
Explanation
Add equationsC+ O2 → CO2 , ΔHfo=- 393.0 kJ/mol and 2( S+ O2 → SO2 , ΔHfo=- 287.0 kJ/mol) Resultant is C+ 2S + 3O2 → CO2 + 2SO2 ( -393 - 2×287=-967 kJ ) By subtracting C + 2S → CS2 , ΔHfo=+ 117.0 kJ/mol from above equation we get CS2 + 3O2 → CO2 + 2SO2 ( -967 - 117=-1084 kJ /mol)Answer: (b)
Q.14
When water is added to conc. H2SO4 it gets very hot. This happens because dilution of conc. H2SO4 is .... [ NCERT 1984]
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a) an exothermic reaction
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b) an endothermic reaction
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c) photochemical reaction
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d) hydrolytic reaction
Explanation
Answer: (a)
Q.15
The ΔHfo for CO2(g), CO(g) and H2O(g) are -393.5, -110.5 and -241.8 kJ/mol respectively. The standard enthalpy change ( in kJ) for the reactionCO2(g) + H2(g) → CO(g) + H2O(g) is ... [ IIT 2000]
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a) 524.1
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b) 41.2
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c) -262.5
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d) -41.2
Explanation
ΔH=[ΔH(CO) + ΔH(H2O)] - [ΔH (CO2) + ΔH(H2) ΔH=[ -110.5 + (-241.8)] - [ -393.5 + 0]ΔH=41.2 kJAnswer: (b)
Q.16
The enthalpy of formation for C2H4(g), CO2(g) and H2O(l) at 25°C and 1atm pressure are 52, -394, -286 kJ/mol respectively. The enthalpy oc combustion of C2H4(g) will be .. [ CBSE PMT 1995]
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a) + 1412 kJ/mol
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b) -1412 kJ/mol
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c) + 141.2 kJ/mol
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d) -141.2 kJ/mol
Explanation
C2H4 + 3O2 → 2CO2 + 2H2OΔHreaction=[2×ΔH (CO2) + 3 ΔH (H2O) - [ ΔH(C2H4 + 3×ΔH(O2)=[ 2×(-394) + 2(-286)] - [ 52 + 0]=-1412 kJAnswer: (b)
Q.17
For which of the following process will energy be absorbed? [ NCERT 1983]
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a) Separating an electron from an electron
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b) Separating a proton from proton
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c) Separating a neutron from neutron
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d) separating an electron from neutral atom
Explanation
Answer: (d)
Q.18
Which one of the following conditions will favour maximum formation of the product in the reaction, ... [NEET 2018] A2 (g) + B2 (g) ⇌ X2 (g) Δr H = – X kJ ?
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a) High temperature and high pressure
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b) Low temperature and low pressure
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c) Low temperature and high pressure
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d) High temperature and low pressure
Explanation
Answer: (c)
0 h : 0 m : 1 s
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