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

Question

The heat energy associated with a change in 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 specific heat in joules per gram-degree Celsius, J/(g degree C), and Delta T is the temperature change in degree celsuis. 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 joule per gram. The constants for H_2O are shown here: How much heat energy, in is required to convert 76.0 g of ice at 18.0 degree C to water at 25.0 degree C?

Explanation / Answer

-18oC --------------------> 0oC ------------------> 25oC

                (1)                  (2)           (3)

there are 3 steps involved in this process

(1) ice from -18 to 0oC

q1 = m Cp dT = 76 x 2.09 x (0 +18) = 2859,12 J

(2) at fusion:

q2 = m delta H   = 76 x 334 = 25384 J

(3) from   0 to 25 oC

q3 = m Cp dT = 76 x 4.18 x 25 = 7942 J

total heat q = q1 + q2 +q3

q   = 36185.12 J

q = 3.62 x 10^4 kJ

heat = 3.62 x 10^4 kJ

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