Question

Liquid sodium is being considered as an engine coolant. How many grams of liquid sodium (minimum) are needed to absorb 5.10 MJ of energy (in the form of heat) if the temperature of the sodium is not to increase by more than 10.0 °C? Use CP= 30.8 J/(K·mol) for Na(l) at 500 K.

Answer 1

energy absorbed = moles of liquid sodium* specific heat* temperatue difference

given that the temperature difference should not exceed 10 deg.c

given eenrgy to be absorbed= 5.1 MJ= 5.1*106 Joules = moles of liquid soldium* 30.8*10

moles of liquid sodium =5.1*10⁶/ (10*30.8)= 16558.44 moles

moles = mass/atomic weight= mass/23

mass = moles*atomic weight of sodium = 16558.44*23 gm =380844.2 gm

since 1000 gm =1 Kg, mass of liquid sodium = 380844.2/1000 =380.86 kg, since temperature rise can be more than 10 deg.c, this amount is the required amount of liquid sodium metal.