21485.The amount of the heat released when 20 ml 0.5 M NaOH is mixed with 100 ml 0.1 M HCl is $x$ kJ. The heat of neutralization is
– 100 $x$ kJ/mol
– 50 $x$ kJ/mol
+ 100 $x$ kJ/mol
+50 $x$ kJ/mol
21486.In a fuel cell methanol is used as fuel and oxygen gas is used as an oxidizer. The reaction is
CH3OH(l) + $\dfrac{3}{2}$O2(g) → CO2(g) + 2H2O(l)
At 298 K standard Gibb's energies of formation for CH3OH(l), H2O(l) and CO2(g) are –166.2, –237.2 and –394.4 kJ mol–1 respectively. If standard enthalpy of combustion of methanol is –726 kJ mol–1, efficiency of the fuel cell will be
87%
90%
97%
80%
21487.The enthalpy of vaporization of a certain liquid at its boiling point of 35ºC is 24.64 kJ mol–1. The value of change in entropy for the process is
704 J K–1mol–1
80 J K–1mol–1
24.64 J K–1mol–1
7.04 J K–1mol–1
21488.In view of the signs of ΔrG° for the following reactions
PbO2 + Pb → 2PbO, ΔrG° < 0
SnO2 + Sn → 2SnO, ΔrG° > 0
Which oxidation states are more characteristic for lead and tin?
For lead +2, for tin +4
For lead +4, for tin +2
For lead +2, for tin +2
For lead +4, for tin +4
21489.The value of ΔH for cooling 2 mole of an ideal monoatomic gas from 225°C to 125°C at constant pressure will be (given Cp = 5/2 R)
250 R
–500 R
500 R
–250 R
21490.The standard enthalpy of formation of NH3 is –46.0 kJ mol–1. If the enthalpy of formation of H2 from its atoms is –436 kJ mol–1 and that of N2 is –712 kJ mol–1, the average bond enthalpy of N—H bond in NH3 is
–1102 kJ mol–1
–964 kJ mol–1
+352 kJ mol–1
+1056 kJ mol–1
21491.Assuming enthalpy of combustion of hydrogen at 273 K, –286 kJ and enthalpy of fusion of ice at the same temperature to be + 6.0 kJ, calculate enthalpy change during formation of 100 g of ice
+1622 kJ
–1622 kJ
+292 kJ
–292 kJ
21492.When compared to ΔG° for the formation of Al2O3, the ΔG° for the formation of Cr2O3 is
higher
lower
same
unpredicted
21493.Standard enthalpy of vapourisation ΔvapHΘ for water at 100°C is 40.66 kJ mol–1. The internal energy of vapourisation of water at 100°C (in kJ mol–1) is (Assume water vapour to behave like an ideal gas)
+43.76
+40.66
+37.56
–43.76
21494.On the basis of the following thermochemical data:
(ΔfG°H+(aq) = 0)
H2O (l) → H+ (aq) + OH– (aq); ΔH = 57.32 kJ
H2 (g) + $dfrac{1}{2}$O2 (g) → H2O (l); ΔH = –286.20 kJ
The value of enthalpy of formation of OH– ion at 25°C is–22.88 kJ
–228.88 kJ
+228.88 kJ
–343.52 kJ