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The heat energy associated with a change in temperature that does not involve a

ID: 1070487 • Letter: T

Question

The heat energy associated with a change in temperature that does not involve a change in phase is given by q = ms delta T where q is heat in joules, m is mass in grams, s is spocific heat in joules por gram dogroe Celsius, J/(g middot degree C), and degrees Celsius. The heat energy associated with a change in phase at constant temperature is given by q = m delta H where q is heat in joules, m is mass in grams, and delta H is the enthalpy in joules per gram. The constants for H_2O are shown here: Specific heat of ice = 2.09 J/(g middot degree C) Specific heat of liquid water = 4.18 J/(g middot degree C) Enthalpy of fusion (H_2O(s) rightarrow H_2O(1). delta H_(= 334 J/g Enthalpy of vaporization (H_2O(1) rightarrow H_2O(g)): delta H_vap = 2250 J/g How much heat energy, in kilojoules, is required to convert 66 0 g of ice at - 180 degree C to water at 25.0 degree C? Express your answer to three significant figures and include the appropriate units.

Explanation / Answer

mass of ice = 66.0 g

Energy required to raise ice from -18 to 0 degrees Celsius:

Q = m Cp t

Q = 66 g x 2.09 J/g C x (0 - (-18)) C

Q1 = 2482.92 J

Energy required to completely melt the ice:

Heat of fusion for water: 334J / kg.

Q2 = Hf x m

Q2= 334 x 66

Q2 = 22044 J

Energy required to raise water from 0 to 25 Celsius:

Q3 = 66 g x 4.18 J/g*C x 25 C

Q3 = 6897 J

total heat required = Q1 + Q2 + Q3

                              = 2482.92 J + 22044 J + 6897 J

                              = 31423.92 J

total heat required = 31.4 kJ