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27 July, 16:12

Plutonium isotopes undergo decay, producing heat. Plutonium isotope 239 (Pu-239) has 1.9 watts per kilogram [W/kg] of decay heat. How much heat, in units of calories [cal], will 1.25 moles [mol] of Pu-239 release after decaying for three hours [h]

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  1. 27 July, 16:22
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    1495.81 calories = 1500 calories to 2 s. f

    Explanation:

    1.9 Watts of decay heat is released for every kilogram of Pu-239 that decays.

    1.25 moles of Pu-239 will release which amount of heat in 3 hours (calories)

    First of, we calculate how much mass of Pu-239 is contained in 1.25 moles of Pu-239.

    Molar mass of Pu-239 = 244 g/mol = 0.244 kg/mol

    1.25 moles of Pu-239 = 1.25 * 0.244 = 0.305 kg

    1 kg of Pu-239 is equivalent 1.9 Watts

    0.305 kg of Pu-239 will give (0.305*1.9/1) Watts; 0.5795 Watts.

    Note: Watts is J/s

    Power = Energy/time

    Energy = power * time

    Power = 0.5795 Watts

    Time = 3 hours = 3*3600 s = 10800 s

    Energy = 0.5795 * 10800 = 6258.6 J

    1 J = 0.239 calorie

    6258.6 J = 6258.6 * 0.239 = 1495.81 calories
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