29. What is E for a system which has the following two steps: Step 1: The system absorbs 60 J of heat while 40 J of work are
performed on it.
Step 2: The system releases 30 J of heat while doing 70 J of work.
C. 90 J
A. 110J
B. 100 J
D. Zero

Zero

Explanation:

Recall that;

E = q + w

Where;

q = heat, w = work done

When heat is absorbed by the system q is positive

When heat is evolved by the system q is negative

When the system does work, w is negative

When work is done on the system w is positive

Step 1

ΔE1= 60 KJ + 40 KJ = 100KJ

Step 2

ΔE2= (-30 KJ) + (-70 KJ) = (-100) KJ

ΔE1 + ΔE2= 100KJ + (-100) KJ = 0KJ