Lecture 22 - Thermochemistry

Tuesday, April 9, 2024

9:00 AM

 

 

 A theory is the more impressive the greater the simplicity of its premises is, the more different kinds of things it relates, and the more extended is its area of applicability. Therefore the deep impression which classical thermodynamics made upon me. It is the only physical theory of universal content concerning which I am convinced that within the framework of the applicability of its basic concepts, it will never be overthrown. — Albert Einstein Class notes (1-21): https://bricejurban.github.io/CHEM101/ Assignments this week: ﷟HYPERLINK "https://boisestatecanvas.instructure.com/courses/28698/assignments/1016549"HW 14 Heat and Phase Changes due Monday Take ﷟HYPERLINK "https://boisestatecanvas.instructure.com/courses/28698/modules/items/3048351"Practice Test for Midterm 4 Read Chapter 5.7, 7.7, and 7.8. If time we may start chapter 8 Reminders: ﷟HYPERLINK "https://boisestatecanvas.instructure.com/courses/28698/assignments/967944"Midterm 4 is next Tuesday 4/16 and covers Lectures 18-23 Equilibrium, Gas Laws, Heat and Phase Changes My CIC (EDUC 107) Hours: Friday 11AM - 1PM Office Hours (SCNC 314 or Zoom): ﷟HYPERLINK "https://calendly.com/bricejurban/office-hours"By appointment Today (4/4) Phase Changes Heat and Work Calorimetry Heat during Phase Transitions Enthalpies of Reaction Thursday (4/11) Phase Diagrams Acids, Bases & Titrations (if time) Phase Changes Untitled picture.png Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings
Untitled picture.png Process Before Energy Change After Endo/exothermic Melting Ice Freezing Water Heat and Work Chemical reactions involve the transfer of energy between system and surroundings. The study of these energy transfers is known as Thermochemistry The system is the chemicals in the reaction and the surroundings is everything else (solvent, or the container, or the air). The term heat refers to the energy transfer from a warmer object to a cooler object until the temperatures are the same. Another form of energy transfer is work which results from the action of a force through a distance The units of heat (q) and work (w) are joules (J) or calories (cal) and the conversion is 1 cal = 4.184 J 1 Food Calorie (1 kcal) (Cal) = 1000 calories 1 Kilojoule (kJ) = 1000 J Energy as heat transfer (q) Energy as work (w) Untitled picture.png Machine generated alternative text: q System Exothermic process Solution (surroundings) Temperature increased Solution (surroundings) q System Endothermic process q q Solution (surroundings) Temperature decreased Solution (surroundings) Untitled picture.png Machine generated alternative text: Force (F) A = area Of face mal Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings
Untitled picture.png Machine generated alternative text: q System Exothermic process Solution (surroundings) Temperature increased Solution (surroundings) q System Endothermic process q q Solution (surroundings) Temperature decreased Solution (surroundings) Untitled picture.png Machine generated alternative text: Force (F) A = area Of face mal The piston can expand or be compressed By convention, energy released by a system is negative, and energy absorbed by a system is positive. q is given a negative (-) sign when the system releases heat to the surroundings (exothermic); q is given a positive (+) sign when the system absorbs heat from the surroundings (endothermic). w is given a negative (-) sign when the system does work on the surroundings (expansion); w is given a positive (+) sign when the surroundings does work on the system (compression). Untitled picture.png Machine generated alternative text: q < O (exothermic) q > O (endothermic) w < O (expansion) System w > O (compression) Surroundings Explain the following, describing how energy of the system changes as a result of the process A cup of hot coffee cools as it equilibrates with the room. Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings
The temperature of the skin decreases when sweat evaporates. Water in a syringe boils when the volume of the syringe increases. The Measurement of Heat Transfer (Calorimetry) Calorimetry is the measure of heat is transferred due to: the difference in temperatures between two substances A substances resistance to temperature changes is known as the heat capacity When heat capacity has the units ____________ it is referred to as _____________ When heat capacity has the units ____________ it is referred to as _____________. Untitled picture.png Machine generated alternative text: copper block specific heat of copper aluminum block specific heat Of aluminum water specific heat Of water Specific Heat Capacity - warms up and cools down quickly as takes much less energy to change its temparature Specific Heat Capacity - warms up and cools down slowly as it takes up much more energy to change its temperature Substance Phase Specific heat capacity, cP J⋅g−1⋅K−1 Molar heat capacity, CP,m J⋅mol−1⋅K−1 Air (typical room conditions) gas 1.012 29.19 Argon gas 0.5203 20.7862 Carbon dioxide CO2 gas 0.839 36.94 Helium gas 5.1932 20.7862 Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings The sweat requires an input of heat from the body so that sweat can transition from a liquid to a gas (vaporization). Therefore the body decreases in temperature, because this pulls heat away. Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings
Untitled picture.png Machine generated alternative text: copper block specific heat of copper aluminum block specific heat Of aluminum water specific heat Of water Specific Heat Capacity - warms up and cools down quickly as takes much less energy to change its temparature Specific Heat Capacity - warms up and cools down slowly as it takes up much more energy to change its temperature Helium gas 5.1932 20.7862 Hydrogen gas 14.30 28.82 Hydrogen sulfide H2S gas 1.015 34.60 Methane CH4 at 2 °C gas 2.191 35.69 Nitrogen gas 1.040 29.12 Neon gas 1.0301 20.7862 Oxygen gas 0.918 29.38 Water at 100 °C (steam) gas 2.03 36.5 Ammonia NH3 liquid 4.700 80.08 Ethanol C2H5OH liquid 2.44 112 Water at 25 °C liquid 4.1816 75.34 Aluminium solid 0.897 24.2 Copper solid 0.385 24.47 Glass solid 0.84 Gold solid 0.129 25.42 Iron solid 0.449 25.09 Lead solid 0.129 26.4 Paraffin wax C25H52 solid 2.5 (avg) 900 Silver solid 0.233 24.9 Steel solid 0.466 Uranium solid 0.116 27.7 Water at −10 °C (ice) solid 2.05 38.09 A calorimeter is used to measure the heat of chemical reactions, physical changes and heat capacity Constant pressure calorimeters measure the change in heat of a reaction occurring in solution. The heat transfer at constant pressure qp is known as the enthalpy change ΔH. Constant volume (bomb) calorimeters resists change in volume and are used to measures the change in heat of combustion reactions. The heat transfer at constant volume qv is known as the internal energy change ΔU. A calorimeter can also measure the specific heat capacity (c) of a substance at constant pressure cP or at constant volume cV. For instance a hot metal (M) transfers heat (q) to the cool water bath (W) until both are at equilibrium. The change in temperature can be measured to find c. CNX_Chem_05_02_Calorim.jpg Untitled picture.png Machine generated alternative text: Motorized stirrer Ignition wires Heat Thermometer Insulated container Sealed bomb 02(g) Sample cup Water Untitled picture.png Machine generated alternative text: System Surroundings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings
CNX_Chem_05_02_Calorim.jpg Untitled picture.png Machine generated alternative text: Motorized stirrer Ignition wires Heat Thermometer Insulated container Sealed bomb 02(g) Sample cup Water Untitled picture.png Machine generated alternative text: System Surroundings If Beaker A contains 50.0 g of water (cp = 4.18 J/g·°C) and Beaker B contains 50.0 g of acetone (cP = 2.15 J/g·°C), both at the same temperature. If both beakers are heated with the same amount of energy, which liquid will have the higher final temperature? The equations for heat transfer are: How much energy is released when 20.0 g of water is cooled from 50°C to 30°C? (cP, water = 4.18 J/g·°C) Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings Ink Drawings
How much energy is released when 20.0 g of water is cooled from 50°C to 30°C? (cP, water = 4.18 J/g·°C) When a 50.0 g block of copper was heated with 1046 J of energy, the temperature increased from 10.0°C to 64.3°C. What is the specific heat of copper? What is the final temperature when a 90.0 g of aluminum at 20°C releases 500 J of energy? (cP,Al = 0.897 J/g·°C ) A 31.1 g wafer of pure gold (cP, Au = 0.129 J/g·°C) initially at 69.3 °C is submerged into 64.2 g of water (cP, water = 4.18 J/g·°C) at 27.8 °C in an insulated container. What is the final temperature of both substances? 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Heat transfer during Phase Transitions (Heating and Cooling Curves) (pick up here on Thursday) During the process of melting energy is needed to change a substance from ___________ to ____________ At constant pressure this is known as the __________ of _________ (ΔHfus) and is typically given in kJ/mol The opposite process is known as ______________________ and the energy change is equivalent to __________ A related process that requires much more energy is the enthalpy of vaporization (__________ to ________) (ΔHvap) The opposite process is known as ______________________ and the energy change is equivalent to __________ These are latent heat processes meaning the phase change occur at constant temperature Substance Molar Heat of fusion (kJ/mol) Melting point (°C) Molar Heat of vaporization (kJ/mol) Boiling point (°C) Ammonia (NH3) 5.6572 −77.74 23.32 −33.34 Carbon dioxide (CO2) 8.10 −78 25.3 -78.46 Hydrogen 0.12 −259 0.917 −253 Lead 4.8 327.5 180 1750 Methane (CH4) 0.95 −182.6 8.20 −161.6 Nitrogen 0.720 −210 5.60 −196 Oxygen 0.445 −219 6.82 −183 Water 6.02 0 40.80 100 How much energy is required to melt 20.0 g of lead at -259 °C? Ink Drawings
How much heat is released by the condensation of 2.88 mols of oxygen at -183 °C? When studying the energy required to transition between phases, it is useful to plot the temperature versus energy. When energy is absorbed by the system this is known as a ____________________ and when it is released by the system it is a _____________________ Untitled picture.png Machine generated alternative text: heat (J)
Find the energy required for 20.0 g of ice at -10 °C to change to steam at 130 °C. Enthalpy (Heat) of Reactions The heat given off by a chemical reaction or required for a reaction to occur at constant pressure is known as the enthalpy of reaction ΔHrxn This energy can be measured using a calorimeter and is useful for determining how much of a substance is needed for a certain amount of heat to be delivered, or how much heat is needed to initiate a reaction. The ΔHrxn is typically given in terms of kJ and written to the right of a chemical reaction. For each of the following reactions, the enthalpy change written is that measured when the numbers of moles of reactants and products taking part in the reaction are as given by their coefficients in the equation. Calculate the enthalpy change when 1.00 gram of the underlined substance is consumed or produced. (a) 4 Na(s) + O2 (g) → 2 Na2O(s) ΔH = -828 kJ
(b) H2(g) + 2 CO(g) → H2O2(l) + 2 C(s) ΔH = +33.3 kJ Phase Diagrams of Pure Substances (Plots of substances Pressure vs Temperature) Phase Diagram for CO2 CO2-phase.png Machine generated alternative text: solid liquid riple point supercritical fluid critical point gas Given a pressure and a temperature you can find the stable phase (gas, solid, or liquid) As pressure and temperature are varied CO2 behaves as expected: As temperature increases you go from solid to liquid to gas As pressure increases you go from gas to solid or gas to liquid or liquid to solid The key to a phase diagram is the phase transition lines.  For example, in the lower left portion of the diagram is the sublimation line that divides the solid and the gas.  At the interface between the solid and the liquid is the melting line.  The interface between liquid and gas is the vaporization line
Phase Diagram for Water (H2O) phase-diagram-water.png Machine generated alternative text: water Ice steam water vapor normal freezing point • normal boiling point O triple point D critical point Note how the solid/liquid line (ice/water line) has a negative slope! This means that you can melt ice by applying a higher pressure. Most substances (like CO2 above) have a positive solid/liquid line Phase Diagram for Carbon Carbon-phase-diagramp.svg.png Machine generated alternative text: Diamond Diamond + Metastable Graphite Graphite + Metastable Diamond Liquid Metaät* Liqui Graphite Vapor 4600 ± 300 K, 10 8±0.2 MPa The phase diagram for carbon is more complicated because solid carbon can exist as multiple allotropes, notably, diamond and graphite. The formation of diamond only occurs under extreme pressure conditions.
Carbon-phase-diagramp.svg.png Machine generated alternative text: Diamond Diamond + Metastable Graphite Graphite + Metastable Diamond Liquid Metaät* Liqui Graphite Vapor 4600 ± 300 K, 10 8±0.2 MPa The formation of diamond only occurs under extreme pressure conditions. Study of this phase diagram suggests that diamonds are not forever. The most stable form at atmospheric conditions is graphite (pencil lead) More explanation of these diagrams can be found here: ﷟HYPERLINK "https://chem.libretexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supplemental_Modules_%28Physical_and_Theoretical_Chemistry%29/Equilibria/Physical_Equilibria/Phase_Diagrams_for_Pure_Substances"Phase Diagrams for Pure Substances - Chemistry LibreTexts

 

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