Calculate e and determine whether the process is endothermic or exothermic for the following cases:
(a) q = 0.763 kj and w = -840 j.
(b) a system releases 66.1 kj of heat to its surroundings while the surroundings do 44.0 kj of work on the system.

a) ∆E=-0.077KJ (exothermic)

b) ∆E = 110KJ (endothermic)

Explanation:

a) ∆E = q + w

q= 0.763 KJ

w= -840J = -0.840 KJ

∆E = 0.763-0.840 = - 0.077KJ

Exothermic reaction are those reactions that proceeds with the release of heat to the surroundings and Energy is negative in exothermic processes.

b)/∆E = q+w

q= 66.1KJ, w=44KJ

∆E = 101KJ

And it is endothermic

When work is done on a system, the international energy increases.

a) E= -0.077KJ Exothermic

b) E= -22.1KJ Exothermic

Explanation:

a) change internal energy E = q+ w

Since q= 0.763KJ and w=-840j= -0.84KJ

E= 0.763kj - 0.84kj

E= -0.077KJ

The process is exothermic since it releases heat to the surrounding i.e E is negative.

b) q= - 66.1KJ negative because it's heat released to the surrounding

w= 44.0KJ work done on the system by the surrounding.

E= q+w

E= -66.1KJ + 44.0KJ

E= -22.1KJ

The process is exothermic because the value of E is negative.

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explanation:

c is the answer because when something is left after something evaporates that shows the chemical change.