Question

how much energy in calories is released when 41.0 g of water at 55.0 celcius is cooled to 0.0 and frozen to solid ice at 0.0

Answer 1

now

consider the step 1

heat released when water goes from 55 C to 0 C

so

Q1 = m x s x dT

given

m = 41 g

specific heat of water = 4.184 J/g/C

dT = Tf - Ti

so

Q1 = 41 x 4.184 x ( 0-55)

Q1 = -9434.92 J

negative sign indicates that energy is released

now

water at 0 c to frozen to ice at 0 C

so

heat released is given by

Q2 = m x Lf

latent heat of fusion of water (Lf) = 334.774 J/g

so

Q2 = -41 x 334.774

Q2 = -13725.734 J

so

total heat released = Q1 + Q2

Q = -9434.92 - 13725.734

Q = -23160.654 J

Q = -23.16 kJ

so

-23.16 kJ of heat is released