A sample of a solid substance has a mass of 0.410 kg. Starting from 20 deg C, it
ID: 1633599 • Letter: A
Question
A sample of a solid substance has a mass of 0.410 kg. Starting from 20 deg C, it is gently heated to 400 degrees as shown in the graph below. (The horizontal axis indicates minutes. Each minute shown corresponds to 45000 Joules of heating.) Table fill in: Melting temperature: _________ degrees. Boiling temperature: _______ degrees. specific heat of liquid phase: ________ J/kg deg degree specific heat of vapor phase: _________ J/kg deg degree latent heat of fusion/melting: _________ J/kg. latent heat of vaporization: _______ J/kg.Explanation / Answer
a. the first horizontal line is the meltin zone, melting temperature = 200 C
b. the second horizontal line is the boiling temperature = 300 C
c. if heat H is provided to mass m of a substance
H = mC(dT)
dH/dt = mC(dT/dt)
m = 0.41 kg
dH/dt = 45000 Joules per minute = 45000/60 W
dT/dt = (300 - 200 ) /8*60 [ betwwen the melting line and the boilinjg line]
C = 750/0.41*0.20833 = 8780.4878 J / kg K
d. similiarly from last part
if heat H is provided to mass m of a substance
H = mC(dT)
dH/dt = mC(dT/dt)
m = 0.41 kg
dH/dt = 45000 Joules per minute = 45000/60 W
dT/dt = (400 - 300 ) /2*60 [ betwwen the melting line and the boilinjg line]
C = 750/0.41*0.833 = 2195.1219 J / kg K
e. Latent heat of melting = L
so, H = mL
L = H/m = 45000*9/0.41 = 987804.87 J/kg [ considering the first horizontal part of the graph]
e. Latent heat of vappourisation = L
so, H = mL
L = H/m = 45000*13/0.41 = 1426829.268 J/kg [ considering the second horizontal part of the graph]