Initial data: ν (number of moles of monoatomic gas) = 5 mol; Т (absolute temperature of a monatomic gas) = 27 ºС = 27 + 273 К = 300 K.
Constants: i (the number of degrees of freedom of a monatomic gas) = 3; R (universal gas constant) = 8.31 J / (mol * K)).
The internal energy of this gas can be determined by the formula: U = i / 2 * ν * R * T.
Let’s perform the calculation: U = 3/2 * 5 * 8.31 * 300 = 18697.5 J ≈ 18.7 kJ.
Answer: The internal energy of 5 mol of this monatomic gas is 18.7 kJ.
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