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Chemistry · The first law of thermodynamics: Concept of work, heat, internal energy and enthalpy, heat capacity, molar heat capacity

5 moles of oxygen are heated at constant volume from to The change in internal e

5 moles of oxygen are heated at constant volume from \( 10^{0} C \) to \( 20^{0} C . \) The change in internal energy of the gas is: \( C_{p}=7.03 \mathrm{cal} \mathrm{mol}^{-1} \mathrm{K}^{-1} \) and \( R= \) \( 8.31 J \mathrm{mol}^{-1} \mathrm{K}^{-1} \)

  • A. 125 call \( l \)
  • B. 252 call
  • C. 50 call
  • D. 500 call

Step-by-step solution

For constant volume, ΔU = n Cv ΔT. Using Cp - Cv = R, convert R to cal: 8.31 J/mol·K ÷ 4.184 J/cal = 1.986 cal/mol·K. So Cv = 7.03 - 1.986 = 5.044 cal/mol·K. ΔT = 10 K, n = 5, thus ΔU = 5 × 5.044 × 10 = 252.2 cal ≈ 252 cal.
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