
# Define the constants
n = 2.5  # in mol
C_v_m = 12.47  # in J/mol/K
T_i = 325  # in K
T_f = 268  # in K
R = 8.314  # in J/mol/K

# Calculate ΔU
delta_U = n * C_v_m * (T_f - T_i)
delta_U /= 1000  # convert to kJ

print(delta_U)
