Question

Which scenario will result in the greatest decrease in energy for the system?

(a) The system releases 234 cal of heat and has 430 J of work done to it.

(b) The system gains 904 J of heat and does 23.9 cal of work.

(c) The system does 321 cal of work and loses 2.34 kJ of heat.

(d) The system has 1.09 kJ of work done to it and loses 892 cal of heat.

(e) The system gains 1000. cal of heat and does 4.814 kJ of work.

Answer 1

delta U = q+ W
1 cal = 4.184 J
a)
q = -234 cal = -234/4.184 = -55.9 J
W= + 430 J
delta U = q+ W
               = -55.9 + 430
               = 374.1 J
b)
q = + 904 J
W= -23.9 cal = -23.9 /4.184 = -5.7 J
delta U = q+ W
               = 904-5.7
               = 898.3.3 J
c)
W = -321 cal = -321/4.184 = -76.7 J
Q= -2340 J
delta U = q+ W
               = -2340 - 76.7
               = -2416.7 J

d)
W = -1090 J
Q= -892 cal = -892/4.184 J = -213.2 J
delta U = q+ W
               = -213.2 - 1090
               = -1031.2 J

e)
Q= +100 cal = +100/4.184 J= 23.9 J
W = -4814 J
delta U = q+ W
               = 23.9- 4814
               = -4790.1 J

Answer: e since it is maximum negative