- #1
grangr
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Homework Statement
If Cp for an ideal gas is 35.4 J/mol⋅K, which of the following is Cv for this gas?
a. 12.5 J/mol⋅K
b. 20.8 J/mol⋅K
c. 29.1 J/mol⋅K
d. 27.1 J/mol⋅K
e. 43.4 J/mol⋅K
b. 20.8 J/mol⋅K
c. 29.1 J/mol⋅K
d. 27.1 J/mol⋅K
e. 43.4 J/mol⋅K
Homework Equations
- ΔH = ΔE + Δ(PV) = Q + W + Δ(PV), and for ideal gas, ΔH = nCvΔT + Δ(nRT) = nCvΔT + nRΔT = nCpΔT
- The kinetic energy for a gas: KE = 3/2⋅(nRT)
- From (1) and (2) above, for an ideal gas, Cv = 3/2⋅(R), thus Cp = 5/2⋅(R)
The Attempt at a Solution
Cp = 35.4 J/mol⋅K = 5/2⋅(R)
Cv = 3/2⋅(R) = 21.24 J/mol⋅K
The correct answer is (d). Clearly I am missing something here, and would appreciate your help!