posted by JOHN on .
A pot containing 1.09 liter of water, initially at 18°C, is placed on a 1101 W electric heating element.
(a) How much heat must be supplied to the water to bring it to a boil?
(b) How much heat is necessary to boil all the water away?
What is the minimum time required to boil all the water away?
L = 2260000 J/kg is the heat of vaporization,
ρ =1000 kg/m^3 is the density of the water,
c = 4185.5 J/(kg•K) is heat capacity of water.
Q1 = c•m•ΔT= c•m•ΔT = c•ρ•V •ΔT = =4180•1000•1.09•10^-3•82 = 3.73•10^5 J
Q2 = L•m = L• ρ•V =2260000 • 1000•1.09•10^-3 =2.46•10^6 J
Q = Q1+Q2 = P•t,
t = (Q1+Q2)/P =
= 3.73•10^5+2.46•10^6)/ 1101= 2574 s = =42.89 min.