Question

A.) An ideal gaseous reaction (which is a hypothetical gaseous reaction that conforms to the laws governing gas behavior) occurs at a constant pressure of 35.0 atm and releases 73.8 kJ of heat. Before the reaction, the volume of the system was 7.00 L . After the reaction, the volume of the system was 3.00 L . Calculate the total internal energy change, ΔE, in kilojoules.

B.) It takes 45.0 J to raise the temperature of an 10.6 g piece of unknown metal from 13.0∘C to 24.1 ∘C. What is the specific heat for the metal?

C.)The molar heat capacity of silver is 25.35 J/mol⋅∘C. How much energy would it take to raise the temperature of 10.6 g of silver by 11.6 ∘C?

D.)What is the specific heat of silver?

Answer 1

A)

w = -PV
w = -(35.0 atm)(3.00 L - 7.00 L)
w = 140 L atm
1 L atm = 101.325 J
140 L atm = 140 101.325 J = 14185.5 J = 14.19 kJ

U = q + w

Since heat was released,
U = -73.8 kJ + 14.19 kJ = -59.61 kJ

B)

q = mC_pT

45.0 = 10.6 C_p (24.1 - 13.0)

C_p = 0.382 J/g.^oC

C)

no. of moles of silver = mass/molar mass = 10.6/107.9 = 0.098

q = n C_mT

q = 0.098 25.35 11.6 = 28.89 J

D)

q = m C_pT

28.89 = 10.6 C_p 11.6

C_p = 0.235 J/g.^oC