If ΔH is the change in enthalpy and ΔE, the change in internal energy accompanying a gaseous reaction, then
ΔH is always greater than ΔE
ΔH < ΔE only if the number of moles of products is greater than the number of moles of the reactants.
ΔH is always less than ΔE
ΔH < ΔE only if the number of moles of products is less than the number of moles of the reactants
A reaction occurs spontaneously if
TS < H and both H and S are + ve
TS > H and both H and S are + ve
TS = H and both H and S are + ve
TS > H and H and is +ve and S is -ve
On heating one end of a piece of metal, the other end becomes hot because of
resistance of the metal
mobility of atoms in the metal
energised electrons moving to the other end
minor perturbation in the energy of atoms
According to the third law of thermodynamics which one of the following quantities for a perfectly crystalline solid is zero at absolute zero ?
Free energy
Entropy
Enthalpy
Internal energy
The absolute enthalpy of neutralisation of the reaction
MgO(s) + 2HCI(aq) → MgCI2(aq) + H2O(l) will be
less than -57.33 kJ mol-1
-57.33 kJ mol-1
greater than -57.33 kJ mol-1
57.33 kJ mol-1
The factor of G values is important in metallurgy. The G values for the following reactions at 800oC are given as
S2 (s) + 2O2(g) → 2SO2 (g); G = - 544 kJ
2Zn(s) + S2(s) → 2ZnS(s); G = - 293 kJ
2Zn(s) + O2(g) → 2ZnO(s); G = - 480 kJ
The G for the reaction
2ZnS(s) + 3O2(g) → 2ZnO(s) + 2SO2 (g) will be
-357 kJ
-731 kJ
-773 kJ
-229 kJ
A chemical reaction will be spontaneous if it is accompanied by a decrease in
entropy of the system
enthalpy of the system
internal energy of the system
free energy of the system
Equal volume of molar hydrochloric acid and sulphuric acid are neutralised by dil NaOH solution and x kcal and y kcal of heat are liberated respectively. Which of the following is true ?
x = y
x = 2y
None of these
The enthalpy and entropy change for the reaction
Br2 (l) + CI2 (g) → 2BrCI (g)
are 30 kJ mol-1 and 105 JK mol-1 respectively. The temperature at which the reaction will be in equilibrium is
285.7 K
273 K
450 K
300 K
Assume each reaction is carried out in an open container. For which reaction will ΔH =f ΔE ?
H(g) + Br(g) → 2HBr(g)
C(s) + 2H2O(g) → 2H2 (g) + CO2 (g)
PCI5(g) → PCI3 (g) + CI2 (g)
2 CO (g) + O2 (g) → 2CO2 (g)
