Br2 == 2Br
24% dissociated => n total moles, 0.24 mol*n of Br, and 0.76*n mol of Br2
=> partial pressure of Br, P Br = 0.24 bar, and
partical pressure of Br2, P Br2 = 0.76 bar
kp = (P Br)^2 / P Br2 = (0.24)^2 / 0.76 = 0.0758
The internal energy has the symbol U. Q is positive if heat is added to the system, and negative if heat is removed;
....."W is positive if work is done by the system"........
and negative if work is done on the system.
So, work done by a system is positive.
The computation for this problem is:
(1.55x10^4 / 1.0x10^3) x 19.8 mm Hg
= 15.5 x 19.88 mm Hg
= 308.14 mm Hg decrease
= 308.14 x 0.05 C = 15.407 deg C
deduct this amount to 100
100 – 15.407 = 84.593 C
ANSWER: 85 deg C (rounded to 2 significant figures)
