Question

Which of the following would release the most heat? Assume the same mass of in each...

Which of the following would release the most heat? Assume the same mass of in each case. Specific heats of ice, liquid water, and water vapor are 2.05 J/(g⋅°C), 4.18 J/(g⋅°C), and 2.01 J/(g⋅°C) respectively, the heat of fusion of ice is 6.01 kJ/mol, the heat of vaporization of water is 40.7 kJ/mol. (Please show your work)

a. Heating the H2) sample from –14°C to 58°C.

b. Cooling the H2O sample from 18°C to –2.3°C.

c. Cooling the sample from 140°C to 110°C.

d. Cooling the H2O sample from 97°C to 62°C.

e. Cooling the H2O sample from 102°C to 86.0°C

Homework Answers

Answer #1

Solution :-

Lets assume we have 100 g water

Lets calculate the energy released in each case

a)heating water from -14 C to 58 c is the endothermic process therefore it does not release heat.

b) cooling sample from 18C to -2.3 C

q= (m*s*delta T)+(-m*delta Hfus)+(m*s*delta T)

=(100 g * 4.18J/gC*(0C-18C))+(-100g*334J/g)+(100g*2.05J/gC*(-2.3-0))

= -41154 J

c)cooling from 140 c to 110 C

q=m*s*delta T

= 100 g * 2.01J/gC*(110-140)

= -6030 J

d) cooling from 97 C to 62C

q=m*s*delta T

= 100 g * 4.18 J/gC * (62-97)

= -14630 J

e) cooling from 102 c to 86 C

q= (m*s*delta T) +(-m*delta Hvap)+(m*s*delta T)

   = (100g*2.01J/gC*(100-102))+(-100 g * 2259 J/g)+(100g*4.18J/gC*(86-100))

   = -232154 J

Therefore most of the energy is released in the case E

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