Ch.11 - Liquids, Solids & Intermolecular ForcesWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds

Solution: Compounds such as CCl2F2 are known as chlorofluorocarbons, or CFCs. These compounds were once widely used as refrigerants but are now being replaced by compounds that are believed to be less harmful t

Solution: Compounds such as CCl2F2 are known as chlorofluorocarbons, or CFCs. These compounds were once widely used as refrigerants but are now being replaced by compounds that are believed to be less harmful t

Problem

Compounds such as CCl2F2 are known as chlorofluorocarbons, or CFCs. These compounds were once widely used as refrigerants but are now being replaced by compounds that are believed to be less harmful to the environment. The heat of vaporization of CCl2F2 is 289 J/g.

What mass of this substance must evaporate to freeze 210 g of water initially at 21 oC? (The heat of fusion of water is 334 J/g; the specific heat of water is 4.18 J/(g K).)

Solution

The amount of heat released by water during it's freezing is absorbed by CCl2F2 for it to evaporate. This means:

The process of freezing 210 g of water initially at 21 ˚C involves two quantities of heat:

q1 =  Heat decrease the temperature of water from 21 ˚C to 0˚C: Cp, (l) = 4.18 J/(g K).
q2 = Heat completely freeze the water: ΔH˚freezing = –ΔH˚fusion = –334 J/g.

For q1: This amount of heat is given by the equation:

where m = mass of water, Cp, (l) = specific heat capacity of water, ΔT = Tfinal – Tinitial = change in temperature. We're given:

• m = 210 g
• Cp, (l) = 4.18 J/(g K)
• ΔT = 0 – 21 ˚C = –21 ˚C = –21 K

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