PYQSide ExamsMy practice

Thermodynamics · Question 34

AIPMT 2012 (Prelims)MCQMedium📈 Topic in 25% papers+4−1
1

In which of the following reactions, standard reaction entropy change ( S ) is positive and standard Gibb's energy change ( G ) decreases sharply with increasing temperature ?

  1. C(graphite)+ 12O2(g) CO(g)
  2. CO(g)+ 12O2(g) CO2(g)
  3. Mg(s)+ 12O2(g) MgO(s)
  4. 12C(graphite)+ 12O2(g) 12CO2(g)

Answer

(1) C(graphite)+ 12O2(g) CO(g)

Solution

G = H -T S ; G falls sharply with rise in T only when S is large and positive, i.e. when the number of gaseous moles increases.

(1) ng=1- 12=+ 12 S >0

(2) ng=1- 32=- 12 S <0

(3) ng=0- 12=- 12 S <0

(4) ng= 12- 12=0 S 0

Only for C(graphite)+ 12O2(g) CO(g), -T S makes G more negative as T rises (this is why carbon reduces metal oxides at high temperature).

Answer: (1)

AIPMT 2012 (Prelims)

Keep practising — Thermodynamics

2

The enthalpy of fusion of water is 1.435 kcal/mol. The molar entropy change for the melting of ice at 0 C is

  1. 10.52 cal/(mol K)
  2. 21.04 cal/(mol K)
  3. 5.260 cal/(mol K)
  4. 0.526 cal/(mol K)
AIPMT 2012 (Prelims)
3

Standard enthalpy of vaporisation vapH for water at 100 C is 40.66 kJ mol-1. The internal energy of vaporisation of water at 100 C (in kJ mol-1) is

  1. +37.56
  2. -43.76
  3. +43.76
  4. +40.66
AIPMT 2012 (Prelims)
4

Consider the following processes : array|l|c| & H (kJ/mol) \ 12A B & +150 \ 3B 2C + D & -125 \ E + A 2D & +350 \ array For B + D E + 2C, H will be

  1. 525 kJ/mol
  2. -175 kJ/mol
  3. -325 kJ/mol
  4. 325 kJ/mol
AIPMT 2011 (Mains)
5

If the enthalpy change for the transition of liquid water to steam is 30 kJ mol-1 at 27 , the entropy change for the process would be

  1. 10 J mol-1 K-1
  2. 1.0 J mol-1 K-1
  3. 0.1 J mol-1 K-1
  4. 100 J mol-1 K-1
AIPMT 2011 (Prelims)
6

Enthalpy change for the reaction, 4H(g) 2H2(g) is -869.6 kJ The dissociation energy of H-H bond is

  1. -434.8 kJ
  2. -869.6 kJ
  3. +434.8 kJ
  4. +217.4 kJ
AIPMT 2011 (Prelims)
7

Which of the following is correct option for free expansion of an ideal gas under adiabatic condition ?

  1. q = 0, T 0, w = 0
  2. q 0, T = 0, w = 0
  3. q = 0, T = 0, w = 0
  4. q = 0, T < 0, w 0
AIPMT 2011 (Prelims)
8

Match List I (Equations) with List II (Type of processes) and select the correct option.

  1. A - (i), B - (ii), C - (iii), D - (iv)
  2. A - (iii), B - (iv), C - (ii), D - (i)
  3. A - (iv), B - (i), C - (ii), D - (iii)
  4. A - (ii), B - (i), C - (iv), D - (iii)
AIPMT 2010 (Mains)
9

Three moles of an ideal gas expanded spontaneously into vacuum. The work done will be

  1. infinite
  2. 3 Joules
  3. 9 Joules
  4. zero
AIPMT 2010 (Mains)
10

For vaporization of water at 1 atmospheric pressure, the values of H and S are 40.63 kJ mol-1 and 108.8 J K-1 mol-1, respectively. The temperature when Gibbs energy change ( G) for this transformation will be zero, is

  1. 273.4 K
  2. 393.4 K
  3. 373.4 K
  4. 293.4 K
AIPMT 2010 (Mains)
11

The following two reactions are known Fe2O3(s) + 3CO(g) 2Fe(s) + 3CO2(g); H = -26.8 kJ FeO(s) + CO(g) Fe(s) + CO2(g); H = -16.5 kJ The value of H for the following reaction Fe2O3(s) + CO(g) 2FeO(s) + CO2(g) is

  1. +10.3 kJ
  2. -43.3 kJ
  3. -10.3 kJ
  4. +6.2 kJ
AIPMT 2010 (Mains)

All Thermodynamics PYQs →

PDFDownload Thermodynamics PYQs as PDF Free, with answer key and a QR code to every solution — print it or study offline⬇
All NEET Chemistry chapters
Physical ChemistrySome Basic Concepts of ChemistryStructure of AtomStates of MatterThermodynamicsEquilibriumRedox ReactionsSolid StateSolutionsElectrochemistryChemical KineticsSurface Chemistry
Inorganic ChemistryClassification of Elements and Periodicity in PropertiesChemical Bonding and Molecular StructureHydrogens-Block Elementsp-Block Elements (Group 13 & 14)Environmental ChemistryGeneral Principles of Isolation of Elementsp-Block Elements (Group 15–18)d- and f-Block ElementsCoordination Compounds
Organic ChemistryOrganic Chemistry – Some Basic Principles and TechniquesIsomerismHydrocarbonsHaloalkanes and HaloarenesAlcohols, Phenols and EthersAldehydes, Ketones and Carboxylic AcidsAminesBiomoleculesPolymersChemistry in Everyday LifePrinciples Related to Practical Chemistry