In a closed vessel there was some water vapor. After the water vapor dissociated, the temperature decreased by 10%, and the volume by 20%. Find the change in internal energy.
The Attempt at a Solution
Let's state, that not all of water vapor dissociated. Let's say that in the beggining there was [itex]n[/itex] moles of [itex]H_2O[/itex] , and [itex]x[/itex] moles of it dissociated.
Since [itex]xH_2O -> xH_2 + 0,5xO_2[/itex] , then we get [itex]x+0,5x[/itex] moles in total of hydrogen and oxygen combined.The total moles of gas molecules after the dissociation would be [itex](n-x) + (x+0,5x)=n+0,5x[/itex]
Then i can write the ideal gas law before and after the dissociation.
to continue, i have to find x in terms of n , but after solving the above, i get that x is a negative number. Please help !