-6688 J
Explanation:
So for this question we have to use equation q=(m)(c)(deltaT)
Mass=20.0 grams
C=4.18 J/g
delta T= final-initial= 5-85=-80
q=(20.0)(4.18)(-80)
q=-6688 J
the products are less stable than the reactants, i think, im not so good at this kind of stuff XD