Which of the following reactions represents an exothermic reaction?
nh3(g) + 12.0 kcal → ½n2(g) + 3/2h2(g)
ch4 + 2o2 → co2 + 2h2o + 212,800 cal
c + 2s → cs2, δh = 27,550 cal
c(graphite) → c(diamond), δh = 0.45 kcal
2h2o → 2h2 + o2, δh = +58 kcal

answer: the figure is attached herewith.

step-by-step explanation:   we are given to sketch a unit circle and label the terminal points corresponding to

in the attached figure, we have drawn a unit circle, with centre at o(0,0) and radius 1 unit. we have labelled the points a, b, c, d and e corresponding to the angles below

∠aox = 60°,

∠box = 120°,

∠cox = 180°,

∠dox = 240°,

∠eox = 300°.

and the coordinates are a(0.5,1), b(-0.5,1), c(-1,0), d(-0.5,-1) and e(0.5,-1).

thus, the answer is complete.