196) The standard heat of combustion of Al is −837.8 kJ⁄mol at 25^oC. If Al reacts with O₂ at 25^oC, which of the following releases 250 kcal of heat?

197) If at 298 K, the bond energies of C−H, C−C, C=C and H−H bonds are 414, 347, 615 and 435 KJ⁄mol respectively. The value of enthalpy change for the reaction H₂C=CH₂ (g) + H₂ (g) → H₃C−CH₃ (g) at 298 K will be:

198) The internal energy change when a system goes from A to B is 40 kJ⁄mol. If the system goes from A to B by a reversible path and returns to state A by an irreversible path, what would be the net change in internal energy?

199) In which of the following, the reaction proceeds towards completion?

200) At 1000 K, the K_p for the reaction of CO₂ (g) with excess of graphite to form CO (g) is 9 atm. Then the mole % of CO in the equilibrium mixture of gases is: