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Chemistry 17.3. What does the Heat Capacity of an object depend on?. 17.3. Heats of Fusion and Solidification. The quantity of heat absorbed by a melting solid is exactly the same as the quantity of heat released when the liquid solidifies; that is, ∆ H fus = –∆ H solid. 17.3.
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17.3 Heats of Fusion and Solidification • The quantity of heat absorbed by a melting solid is exactly the same as the quantity of heat released when the liquid solidifies; that is, ∆Hfus = –∆Hsolid.
17.3 Heats of Fusion and Solidification • The molar heat of fusion (∆Hfus) is the heat absorbed by one mole of a solid substance as it melts to a liquid at a constant temperature. • The molar heat of solidification (∆Hsolid) is the heat lost when one mole of a liquid solidifies at a constant temperature.
for Sample Problem 17.4 Problem Solving 17.21 Solve Problem 21 with the help of an interactive guide tutorial.
17.3 Heats of Vaporization and Condensation • The amount of heat necessary to vaporize one mole of a given liquid is called its molar heat of vaporization (∆Hvap). • The amount of heat released when 1 mol of vapor condenses at the normal boiling point is called its molar heat of condensation (∆Hcond).
17.3 Heats of Vaporization and Condensation • The quantity of heat absorbed by a vaporizing liquid is exactly the same as the quantity of heat released when the vapor condenses; that is, ∆Hvap = –∆Hcond.
17.3 Heats of Vaporization and Condensation
for Sample Problem 17.5 Problem-Solving 17.24 Solve Problem 24 with the help of an interactive guided tutorial.
17.3 Heat of Solution • During the formation of a solution, heat is either released or absorbed. • The enthalpy change caused by dissolution of one mole of substance is the molar heat of solution (∆Hsoln).
17.3 Heat of Solution • When ammonium nitrate crystals and water mix inside the cold pack, heat is absorbed as the crystals dissolve.
for Sample Problem 17.6 Problem-Solving 17.26 Solve Problem 26 with the help of an interactive guided tutorial.
17.3 Section Quiz. • 17.3.
17.3 Section Quiz. • 1. The molar heat of condensation of a substance is the same, in magnitude, as its molar heat of • formation. • fusion. • solidification. • vaporization.
17.3 Section Quiz • 2. The heat of condensation of ethanol (C2H5OH) is 43.5 kJ/mol. As C2H5OH condenses, the temperature of the surroundings • stays the same. • may increase or decrease. • increases. • decreases.
17.3 Section Quiz • 3. Calculate the amount of heat absorbed to liquefy 15.0 g of methanol (CH3OH) at its melting point. The molar heat of fusion for methanol is 3.16 kJ/mol. • 1.48 kJ • 47.4 kJ • 1.52 103 kJ • 4.75 kJ
17.3 Section Quiz • 4. How much heat (in kJ) is released when 50 g of NH4NO3(s), 0.510 moles, are dissolved in water? ssoln = 25.7 kJ/mol • 12.85 kJ • 13.1 kJ • 25.7 kJ • 1285 kJ