Assume the eccentric professor has a daily special request for her coffee. She l

Question

Assume the eccentric professor has a daily special request for her coffee. She likes to have the 250.0 mL of coffee frozen at -15.0°C overnight and then wants it heated to 95°C when she gets there in the morning.

Hfusion = 6.02 kJ/mol;

Hvaporization = 40.67 kJ/mol;

Csolid = 33.1 J/(molx°C);

Cliquid = 75.4 J/(molx°C);

Cgas = 33.1 J/(mol x °C)

Boiling point = 100°C; and

Melting point = 0°C.

See Section 12.2 and Problems 12.17 and 12.19. Assume coffee and milk have all the physical properties of water.

a. How much heat energy is required to heat the coffee as per the special request?

b. Identify the name and process of each phase change in the coffee

Explanation / Answer

q absorbed = mcoffee*cSOLID*DT +ncoffe*DHffus + mcoffee*cliquid*DT

mcoffee = mass of coffee = 250*1 = 250 grams

no of moles of coffee = 250/18 = 13.9 mole

q absorbed = 13.9*33.1*(-(-15))+13.9*6.02+13.9*75.4*(95-0)

           = 106.6 kj

b. solid ---> liquid (fusion/melting)

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