Question

The heat energy associated with a change in temperature that does not involve a change in phase is given by

q=msΔT

where q is heat in joules, m is mass in grams, s is specific heat in joules per gram-degree Celsius, J/(g⋅∘C), and ΔT is the temperature change in degrees Celsius. The heat energy associated with a change in phase at constant temperature is given by

q=mΔH

where q is heat in joules, m is mass in grams, and ΔH is the enthalpy in joules per gram.

Physical constants

The constants for H2O are shown here:

Specific heat of ice: sice=2.09 J/(g⋅∘C)

Specific heat of liquid water: swater=4.18 J/(g⋅∘C)

Enthalpy of fusion (H2O(s)→H2O(l)): ΔHfus=334 J/g

Enthalpy of vaporization (H2O(l)→H2O(g)): ΔHvap=2250 J/g

Part A

How much heat energy, in kilojoules, is required to convert 63.0 g of ice at −18.0 ∘C to water at 25.0 ∘C ?

Express your answer to three significant figures and include the appropriate units.

Part B

How long would it take for 1.50 mol of water at 100.0 ∘C to be converted completely into steam if heat were added at a constant rate of 15.0 J/s ?

Express your answer to three significant figures and include the appropriate units.

Answer 1