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CBSE Questions for Class 11 Medical Chemistry Thermodynamics Quiz 12 - MCQExams.com

Choose the reaction in which ΔH is not equal to ΔU.
  • C(graphite)+O2(g)CO2(g)
  • C2H4(g)+H2(g)C2H6(g)
  • 2C(graphite)+H2(g)C2H2(g)
  • H2(g)+I2(g)2HI(g)
  • N2(g)+O2(g)2NO(g)
When the total cell emf of a volatic cell is greater than zero, which of the following is true about the reaction quotient Q and free energy change G for the cell reaction?
  • Q is less than one and G is greater than zero
  • Q is greater than one and G is greater than zero
  • Q is less than one and G is less than zero
  • Q is zero and G is greater than zero
  • Q is greater than one and G is less than zero
The enthalpy of combustion for the H2, cyclohexene and cyclohexane are 241,3800 and 3920kJ mol1, respectively. Heat of hydrogenation of cyclohexene is:
  • +121kJ mol1
  • 121kJ mol1
  • +242kJ mol1
  • 242kJ mol1
If ΔHf(H2O) is 285.20 kJ mol1, then ΔHf(OH) is:
  • 227.90 kJ mol1
  • +228.88 kJ mol1
  • 343.52 kJ mol1
  • +343.52 kJ mol1
The densities of graphite and diamond at 298K are 2.25 and 3.31 g cm3 respectively. If the standard free energy difference is 1895 J mol1, the pressure at which graphite will be transformed into diamond is:
  • 9.92×108Pa
  • 9.92×107Pa
  • 9.92×106Pa
  • None of these
At 298 K the entropy of rhombic sulphur 32.04 J/mol K and that of monoclinic sulphur is 32.68 J/mol K. The heat of their combustion are respectively 298246 and 297948J mol1. ΔG for the reaction; SrhormbicSmonoclinic will be :
  • 107.28 J
  • 10.728 J
  • 107.28 kJ
  • 10728 J
Given: S+32O2SO3+2x kcal
           SO2+12O2SO3+y kcal

With the help of the above reactions, find out the heat of formation of SO2.
  • (2xy)
  • (x+y)
  • (2x+y)
  • (2x/y)
A particular reaction at 27oC for which ΔH>0 and ΔS>0 is found to be non-spontaneous. The reaction may proceed spontaneously if:
  • the temperature is decreased
  • the temperature is kept constant
  • the temperature is increased
  • it is carried in open vessel at 27oC
Although the dissolution of ammonium chloride in water is an endothermic reaction, even then it is spontaneous because:
  • ΔH is positive, ΔS is -ve
  • ΔH is +ve, ΔS is zero
  • ΔH is positive, TΔS<ΔH
  • ΔH is +ve, ΔS is positive and ΔH<TΔS
A piece of metal weighing 100 g is heated to 80o C and dropped into 1 kg of cold water in an insulated container at 15o C. If the final temperature of the water in the container is 15.69o C, the specific heat of the metal in J/go.C is:
  • 0.38
  • 0.24
  • 0.45
  • 0.13
The enthalpy of hydrogenation of benzene is 49.8 kcal/mol while its resonance energy is 36.0 kcal/mol. The enthalpy of formation of benzene is:
  • 4.6 kcal
  • 28.6 kcal/mol
  • 85.8 kcal/mol
  • 13.8 kcal/mol
The molar heat capacities of Iodine vapour and solid are 7.8 and 14 cal/mol respective enthalpy of sublimation of iodine is 6096 cal/mol at 200C, then what is ΔH the value  at 250C in cal/mol.
  • 5360
  • 4740
  • 6406
  • none of these
The enthalpy of combustion of methane, graphite and dihydrogen at 298K are 890.3 kJmol1,393.5 kJmol1,285.8 kJmol1 respectively. Enthalpy of formation of CH4(g) will be:
  • 74.8kJmol1
  • 52.27kJmol1
  • +74.8kJmol1
  • +52.26kJmol1
Water is brought to boil under the pressure of 1.0 atm. When an electric current of 0.50 A from a 12 V supply is passed for 300 s through resistance in thermal contact with it is found that 0.798 g of water is vapourised. Calculate the molar internal energy change at boiling point (373.15 K).
  • 37.5kJ mol1
  • 3.75kJ mol1
  • 42.6kJ mol1
  • 4.26kJ mol1
Calculate ΔH0f for UBr4 from ΔG0 of reaction and the S0 values.U(s)+2Br2(l)UBr4(s);ΔG0=788.6KJ;S0(J/Kmol)50.3,152.3,242.6
  • -822.1 KJ/mol
  • -841.2 KJ/mol
  • -775.6 KJ/mol
  • -804.3 KJ/mol
For the reaction, C3H8(g)+5O2(g)3CO2(g)+4H2O(l) at constant temperature, ΔHΔE is:
  • +3RT
  • RT
  • +RT
  • 3RT
If for H2(g)+12O2(g)H2O(g);H1 is the enthalpy of reaction and for H2(g)+12O2(g)H2O(l);H2 is enthalpy of reaction then:
  • H1>H2
  • H1=H2
  • H1<H2
  • H1+H2=0
Ellingham's diagram represents
  • Change of ΔG with temperature
  • Change of ΔH with temperature
  • Change of ΔG with pressure
  • Change of (ΔGTΔS) with temperature
1 mole of ice at 0C and 4.6 mm Hg pressure is converted to water vapour at a constant temperature and pressure. Find ΔH if the latent heat of fusion of ice is 80 Cal/gm and latent heat of vaporization of liquid water at 0C is 596 Cal per gram and the volume of ice in comparison to that of water (vapour) is neglected.
  • 14.53 Kcal/mol
  • 12.16 Kcal/mol
  • 10.22 Kcal/mol
  • 15.62 Kcal/mol
100 ml 0.5N H2SO4 (strong acid) is neutralised with 200 ml 0.2 M NH4OH in a constant pressure Calorimeter which results in temperature rise of 1.4C. If heat capacity of Calorimeter content is 1.5 kJ/C. Which statement is/ are correct:

Given: HCl+NaOHNaCl+H2O+57 kJ
CH3COOH+NH4OHCH3COONH4+H2O+48.1 kJ
  • enthalpy of neutralisation of HCl v/s NH4OH is 52.5 kJ/mol
  • enthalpy of dissociation (ionization) of NH4OH is 4.5 kJ/mol
  • enthalpy of dissociation of CH3COOH is 4.6 kJ/mol
  • H for 2H2O(l)2H+(aq.)+2OH(aq.) is 114 kJ
Fruend and Long were 2 scientists interested in adsorption.
Once in a discussion Fruend asked "I can see adsorption is spontaneous, but why it is always exothermic?"
Long said"_________________"
Choose Long's answer :
  • G > 0 & S < 0 H < 0
  • G < 0 & S < 0 H < 0
  • G > 0 & S > 0 H > 0
  • G , 0 & S > 0 H > 0
Calculate the heat needed to raise the temperature of 20g iron from 25oC to 500oC, if specific heat capacity of iron is 0.45JK1 g1.
  • 6732J
  • 225J
  • 15.66J
  • 2250J
For the reaction taking place at certain temperature NH2COONH4(s)2NH3(g) if equilibrium pressure is 3X bar then ΔG would be:
  • RT ln 93RT ln X
  • RT ln 43RT ln X
  • 3RT ln 4X
  • none of these
A monoatomic ideal gas undergoes a process in which the ratio of P to V at any instant is constant and equals to 1. What is the molar heat capacity of the gas?
  • 4R/2
  • 3R/2
  • 5R/2
  • 0
Which statement is correct?
  • (dHdT)P<(dEdT)V
  • (dHdT)P+(dEdT)V=R
  • (dEdV)T of ideal gas is zero
  • All of these
Calculate the hear needed to raise the temperature of 20g from 25oC to 500oC, if specific heat capacity of iron is 0.45JK1 g1.
  • 4274J
  • 225J
  • 15.66J
  • 2250J
A solid material supplied with heat at a constant rate. The temperature of material is changing with heat input as shown in figure. What does slope DE represents?
770029_61e11a6e2e494229bed77b340bcce338.png
  • latent heat of liquid
  • latent heat of vapour
  • heat capacity of vapour
  • inverse of heat capacity of vapour
The Gibb's energy for the decomposition of Al2O3 at 500oC is as follows:

23Al2O343Al+O2 ;    ΔG=+960 kJ.

The potential difference needed for the electrolytic reduction of aluminium oxide (Al2O3) at 500oC is at least:
  • 4.5V
  • 3.0V
  • 2.5V
  • 5.0V
H2(g)+Cl2(g)=2HCl(g);
ΔH(298K) =22.06kcal. For this reaction, ΔU is equal to:
  • 22.06+2×103×298×2kcal
  • 22.06+2×298 kcal
  • 22.062×298×4 kcal
  • 22.06 kcal
Calculate the heat needed to raise the temperature of 20 g iron from 25C to 500C, if specific heat capacity of iron is 0.45 JK1g1.
  • 15.66 J
  • 4275 J
  • 225 J
  • 2250 J
9.2g of toulene C2H8(l) is completely burnt in air. The difference in heat change at constant pressure and constant volume at 27oC is
  • 2.5kJ
  • +2.5kJ
  • Zero
  • 0.50kJ
A vessel contains 100 litres of a liquid X. Heat is supplied to the liquid in such a fashion that, heat given equals change in enthalpy. The volume of the liquid increases by 2 litres. If the external pressure is one atm, and 202.6 Joules of heat were supplied, then [U total internal energy] :
  • ΔU=0,ΔH=0
  • ΔU=+202.6J,ΔH=+202.6J
  • ΔU=202.6J,ΔH=202.6J
  • ΔU=0,ΔH=+202.6J
H+(aq)+NaOH(aq)Na++H2O(l) H1=1390 cals
HCN(aq)+NaOH(aq)Na++CN+H2O(l) H2=2900 cals.

What is H value for HCN(aq)H+(aq)+CN(aq)?
  • 11400 cals
  • 10790 cals
  • 12500 cals
  • 9800 cals
Ethyl chloride (C2H5Cl), is prepared by reaction of ethylene with hydrogen chloride :
C2H4(g)+HCl(g)C2H5Cl(g);H=72.3kJ/mol
What is the value of U (in kJ), if 70 g of ethylene and 73 g of HCL are allowed to react at 300 K?
  • 69.8
  • 180.75
  • 174.5
  • 139.6
For a certain reaction the change in enthalpy and change in entropy are 40.63 kJ mol1 and 100 JK1. What is the value of Δ at 270C and indicate whether the reaction is spontaneous or not
  • +10630Jmol1; spontaneous
  • +10630Jmol1; non spontaneous
  • 7990Jmol1; spontaneous
  • +7900Jmol1; spontaneous
Stearic acid [CH3 (CH2)16 CO2H] is a fatty acid, the part of fat that stores most of the energy. 1.0 g of stearic acid was burned in a bomb calorimeter. The bomb had a heat capacity of 652 J/C. If the temperature of 500 g water (c=4.18J/g C) rose from 25.0 to 39.3C, how much heat was released when the strearic acid burned? [Given Cp(H0O)=4.18 J/g C]
  • 39.21 kJ
  • 29.91 kJ
  • 108 kJ
  • 9.32 kJ
For which of the following reaction HU:
  • H2(g)+Cl2(g)2HCl(g)
  • N2(g)+3H2(g)2NH3(g)
  • NH4HS(s)NH3(g)+H2S(g)
  • CaCO3(s)CaCO(s)+CO2(g)
For Pt, H2(p1atm) |H(1M)|H2(p2 atm) , Pt (where, p1 and p2 are pressures) cell reaction will be spontaneous if?
  • p1=p2
  • p1>p2
  • p2>p1
  • p1=1atm
For a certain reaction the change in enthalpy and change in entropy are 40.63 kJ ,ol KJ1. What is the value of G at 27C and indicate whether the reaction is spontaneous.
  • +10630 J mol1; spontaneous
  • +10630 J mol1; non spontaneous
  • 7990 J mol1; spontaneous
  • +7900 J mol1; spontaneous
For Ag,¯CP(JK1mol1) is given by 24+0.006 T. If temperature of 3 mol of silver is raised from 27C to its melting point 927C under 1 atm pressure then H is equal to:
  • 52 kJ
  • 76.95 kJ
  • 89.62 kJ
  • 38.62 kJ
What is free energy change (ΔG) when 1.0 mole of water at 100oC and 1 atm pressure is converted into steam at 100oC and 2 atm pressure?
  • 0 cal
  • 540 cal
  • 515.4 cal
  • None of these
The heat capacity of a bomb calorimeter is 300 J/K. When 0.16 gm of methane was burnt in this calorimeter the temperature rose by 3C. The value of U per mole will be
  • 100 kJ
  • 90 kJ
  • 900 kJ
  • 48 kJ
NX is produced by the following step of reactions:
M+X2MX2
3MX2+X2M3X8
M3X8+N2CO3NX+CO2+M3O4
How much M (metal) is consumed to produce 206gm of NX?
(Take atomic weight of M=56,N=23,X=80)
  • 42gm
  • 336gm
  • 143gm
  • 74gm
The heat change during the reaction 24g C and 128g S following the change: 

C+S2CS2;H=22K cal.
  • 22 K cal
  • 11 K cal
  • 44 K cal
  • 32 K cal
100ml of O2 gas diffuses in 10 seconds. 100ml of gas x diffuses in t seconds. Gas x and time t can be respectively:
  • H2,2.5 seconds
  • SO2, 16 seconds
  • CO,10 seconds
  • He, 4 seconds
For a given reaction, ΔH=35.5kJmol1 and ΔS=83.6kJmol1. The reaction is spontaneous at: (Assume that ΔH and ΔS do not vary with temperature)
  • T > 425 K
  • all temperatures
  • T > 298 K
  • T < 425 K
On the basis of the following thermochemical data
H2O(g)H+(aq)+OH(aq);ΔH=57.32kJ
H2(g)+12O2(g)H2O(l);ΔH=286.2kJ
The value of enthalpy of formation of OH ion at 25oC is:
  • +288.88kJ
  • 343.52kJ
  • 22.88kJ
  • 228.88kJ
Heat of reaction for the equation, A(s)+B(g)2C(g) is 40 kJ at 300 K at constant volume. Hence, heat of reaction at constant pressure and at 300 K is___________.
  • 42.5 kJ
  • 37.5 kJ
  • 40.0 kJ
  • 30.0 kJ
If an electron is moving in an orbit with total energy U=e2rr is radius of the orbit then find the speed of the electron.
  • emr
  • eemr
  • er2m
  • 2emr
Eo of an electrode half reaction is related to ΔGo by the equation, Eo=ΔGo/nF. If the amount of Ag+ in the half reaction, Ag++eAg is tripled then:
  • n is tripled
  • ΔGo reduces to one third
  • Eo reduces to one third
  • None of the above
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