Question

calculate the amount of heat to be added to warm 150 g of ice from -5 c to produce steam at 105 c? Show calculation

Answer 1

Amount of heat needed

Q = Q1 + Q2 + Q3 + Q4 + Q5

Q1 = heat needed from -5 C to 0 C ice = m*Ci*dT1

Q2 = heat needed from 0 C ice to 0 C water = m*Lf

Q3 = heat needed from 0 C water to 100 C water = m*Cw*dT2

Q4 = heat needed from 100 C water to 100 C steam = m*Lv

Q5 = heat needed from 100 C steam to 105 C steam = m*Cs*dT3

Given values are

m = 150 gm = 0.15 kg

dT1 = 0 - (-5) = 5

dT2 = 100 - 0 = 100

dT3 = 105 - 100 = 5

Cw = 4186 J/kg-C

Lf = 3.34*10^5 J/kg

Lv = 2.26*10^6 J/kg-C

Ci = 2010 J/kg-C

Cs = 2010 J/kg- C

Using these values

Q = m*Ci*dT1 + m*Lf + m*Cw*dT2 + m*Lv + m*Cs*dT3

Q = m*(Ci*dT1 + Lf + Cw*dT2 + Lv + Cs*dT3)

Q = 0.15*(2010*5 + 3.34*10^5 + 4186*100 + 2.26*10^6 + 2010*5)

Q = 4.55*10^5 J