Question

Determine the amount of energy required (in MJ) to convert 35 g of ice, initially at a temperature of −25°C, to steam at 145°C.

____________________MJ

Answer 1

Specific heat(C_{​​​​​​ice}) = 2.108 J/g-°C, Latent heat of fusion of ice (L) = 334 J/g, Specific heat(C_{​​​​​water}) = 4.184 J/g-°C, Latent heat of Vaporization(V) = 2260 J/g, Specific heat(C_{​​​​​​steam}) = 1.996 J/g-°C

Heat energy required to heat ice from -25°C to 0°C (Q1):

Q1 = mC_{​​​​​ice}​​∆T = (35 g)*(2.108 J/g-°C)*(0°C - (-25°C)) = 1844.5 J

Heat energy required to melt ice (Q2):

Q2 = mL = (35 g)*(334 J/g) = 11690 J

Heat energy required to heat water from 0°C to 100°C(Q3):

Q3 = mC_{​​​​​water}∆T = (35 g)*(4.184 J/g-°C)*(100°C - 0°C) = 14644 J

Heat energy required to Vaporize water(Q4):

Q4 = mV = (35 g)*(2260 J/g) = 79100 J

Heat energy required to heat steam from 100°C to 145°C(Q5):

Q5 = mC_{​​​​​Steam}∆T = (35 g)*(1.996 J/g-°C)*(145°C - 100°C) = 3143.7 J

Total heat required = Q1 + Q2 + Q3 + Q4 + Q5 = 110422.2 J = 0.11 MJ