Suppose 15.2 g of oxygen (O2) is heated at constant atmospheric pressure from 13.3°C to 148°C. (a) How many moles of oxygen are present? (Take the molar mass of oxygen to be 32.0 g/mol) (b) How much energy is transferred to the oxygen as heat? (The molecules rotate but do not oscillate.) (c) What fraction of the heat is used to raise the internal energy of the oxygen?
Diatomic gas Cp = (7/2)R ; Cv = (5/2)R
Q = nCp(Tf - Ti)
W = P(Vf - Vi) = NR(Tf - Ti)
Change in Kinetic Energy = (3/2)nRT
Change in Internal Energy = nCv(Tf - Ti) = Q - W
Cp - Cv = R
The Attempt at a Solution
I believe I got all the information correct above. The ones I'm not too sure about are the Cp and Cv values.
15.2 g O2 (1 mol O2/32 g O2) = .475 mol O2
Change in Internal Energy = (.475 mol O2)((5/2)*8.31 J/mol*K)(148 C - 13.3 C) = 1329.236 J
Change in Kinetic Energy = (3/2)(.475 mol O2)(8.31 J/mol*K)(148 C - 13.3 C) =797.542 J
Fraction of heat used to raise Internal Energy of O2 = 797.542 J/1329.236 J = 0.6
To be honest I'm not really sure about my work on Parts B and C. I was kind of guessing as I was going along. Is the work for those parts correct?