First and second ionisation enthalpies of Mg are 737. 76 and 1450.73 J mol-1 respectively. The energy required to convert all the atoms of magnesium to magnesium ions present in 24g of magnesium vapours is
24 kJ
2.188 kJ
12 kJ
4.253 kJ
Molar heat of vaporisation of a liquid is 6 kJ mol-1. If the entropy change is 16 J mol-1 K-1, the boiling point of the liquid is:
375°C
375 K
273 K
102°C
Consider the reaction,
N2 + 3H2 → 2NH3
carried out at constant temperature and pressure. If H and U are the enthalpy and internal energy changes for the reaction, which of the following expression is true?
H = 0
If standard enthalpies of formation of CaCl (s) (hypothetical) and that of CaCl2 (s) are -188 J mol-1 and -795 kJ mol-1 respectively, calculate the value of standard heat of reaction for the following disproportionation reaction
2CaCl (s) → CaCl2 (s) + Ca (s)
-607 kJ mol-1
+607 kJ mol-1
-419 kJ mol-1
+419 kJ mol-1
For the reaction,
A (g) + 2B (g) → 2C (g) + 3D (g)
the change of enthalpy at 27°C is 19 kcal. The value of E is
21.2 kcal
17.8 kcal
18.4 kcal
20.6 kcal
If Hf (H2O) is -286.20 kJ mol-1, then H (OH-) is
-228.88 kJ mol-1
+228.88 kJ mol-1
-343.52 kJ mol-1
+343.52 kJ mol-1
A.
-228.88 kJ mol-1
H+ + OH- → H2O, H = -57.3 kJ mol-1 (standard value)
H = H°f (H2O) - H°f (H+) - H°f (OH-)
-57.3 = -286.2 - 0 - H°f (OH-)
H°f (OH-) = -228.9 kJ mol-1
1 mole of gas occupying 3 L volume is expanded against a constant external pressure of 1 atm to a volume of 15 L. The work done by a system is equal to
-1.215 × 103 J
-12.15 × 103 J
+1.215 × 103 J
+12.15 × 103 J
Which one of the following equations does not correctly represent the first law of thermodynamics for the given processes involving an ideal gas? (Assume non-expansion work is zero)
Isothermal process : q = -w
Cyclic process : q = -w
Isochoric process : = q
Adiabatic process : = -w