Which is false in this heat of formation question?

Data:


(1) H2(g) + 陆O2(g) 鈫?H2O(g) 螖H = -241.8 kJ


(2) H2(g) + 陆O2(g) 鈫?H2O(l) 螖H = -285.8 kJ


On the basis of the above data, which of the following statements is false?





a. Reaction (1) is exothermic.


b. Reaction (2) is the formation reaction for H2O(l).


c. The reverse of reaction (2) is endothermic.


d. The energy content of H2O(g) is lower than H2O(l).


e. 螖H for the reaction: H2O(l) 鈫?H2O(g) is + 44 kJ/mol.











I feel like a and b are both correct. I believe c to be false, but I'm not sure. I think d may be false, too. Can someone help me understand?Which is false in this heat of formation question?
As the only difference between the two reactions is the physical state of the water produced, it's clear that the difference in the heats of formation reflects the heat or enthalpy of vapourisation of water. In fact a very simple example of Hess's law enables the value to be derived, by reversing the second equation





H2(g) + 陆O2(g) 鈫?H2O(g) . . . . . . . 螖H = -241.8 kJ/mol


. . . . . . H2O(l) 鈫?H2(g) + 陆O2(g) . 螖H = +285.8 kJ/mol


-----------------------------------.--鈥?br>

. . . . . . H2O(l) 鈫?H2O(g) . . . . . . . .螖H = +44.0 kJ/mol





In fact the value I have for the molar heat of vapourisation of water is 40.7 kJ/mol, but this is near enough. Note that Hess's method explicitly states that if you reverse an equation, the sign of the 螖H value must be changed, so an exothermic reaction becomes endothermic, and vice versa.





And this really covers all of your option statements: reaction (1) gives the heat of formation of water in the gas phase, while (2) gives it for the liquid phase. Both are exothermic reactions, but become endothermic if the equation is reversed. From the procedure I gave above, the phase change from liquid water to vapour requires the addition of heat ie it's endothermic, so the heat or energy content in the gas phase is higher (so option d is incorrect). And the heat required - the latent heat of vapourisation - is around +40 kJ/mole (note that strictly speaking the equation in option e is not a reaction, but a change in phase, but that's a minor point).





I hope this is all clear and makes sense to you!Which is false in this heat of formation question?
i wonder if people chillin out on the computer on a sunday afternoon want to help you with your homework.


i myself need at least $20 an hour to tutor.