Final answer:
The energy in joules of 1 mol of gas at 100 degrees Celsius is best approximated by the universal gas constant, which is 8.314 J/mol·K, so the correct answer is A. 8.314 J/mol.
Step-by-step explanation:
The question is asking for the energy in joules of 1 mol of gas at 100 degrees Celsius. Using the heat capacity of gases, we can understand that for an ideal gas, the molar energy can be expressed using the gas constant, which is represented in joules per mole per kelvin (J/mol·K). For an ideal monatomic gas, the molar heat capacity at constant volume (Cv) is approximately 3/2 R and at constant pressure (Cp) is approximately 5/2 R where R is the universal gas constant 8.314 J/mol·K. For the purposes of the question, assuming it asks for either Cv or Cp values, the closest value offered is 8.314 J/mol, which is indeed R, the universal gas constant.
Given this information, and without further context such as whether the gas is monatomic or diatomic, or whether it's at constant volume or pressure, the best answer from the choices provided would be A. 8.314 J/mol, as this is the value closest to the universal gas constant for one mole of an ideal gas.