Specific Heat

Question

Liquid sodium is being considered as an engine coolant. How many grams of liquid sodium (minimum) are needed to absorb 4.00 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.

 

I understand that m= q/Cp(deltaT)

q= 4.00x 10^6 J

m=?

Cp= 30.8 J/k*mol

deltaT=10.0 degrees Celcius (also Kelvin)

Answer 1

You are on the right track. Solve for m using the equation you wrote. Since your Cp is in J/K mol, your m term is in moles. Use the atomic mass of sodium to convert these moles to grams (1 mol sodium = 23 g sodium).

Mass (grams) = 23 g/mol x (4 x 10^6 J)/[(30.8 J/K mol) (10 K)]