FITCH Rules “A” students work (without solutions manual) G1: Suzuki is Success ~ 10 problems/night. G2. Slow me down G3. Scientific Knowledge is Referential General Alanah Fitch G4. Watch out for Red Herrings Flanner Hall 402 G5. Chemists are Lazy 508-3119 [email protected] C1. It’s all about charge Office Hours W – F 2-3 pm C2. Everybody wants to “be like Mike” C3. Size Matters ⎛ qq12⎞ ⎛ qq12⎞ Ekel = ⎜ ⎟ or= k⎜ ⎟ ⎝ rr12+ ⎠ ⎝ d ⎠ Module #11 Chemistry C4. Still Waters Run Deep Thermochemistry C5. Alpha Dogs eat first Energy: capacity to do work Galen, 170 Marie the Jewess, 300 Jabir ibn Galileo Galili Evangelista Abbe Jean Picard Daniel Fahrenheit Blaise Pascal Robert Boyle, Isaac Newton Anders Celsius Hawan, 721-815 An alchemist 1564-1642 Torricelli 1620-1682 1686-1737 1623-1662 1627-1691 1643-1727 1701-1744 1608-1647 wFd= () Or transfer heat, q Charles Augustin James Watt Luigi Galvani Count Alessandro Amedeo Avogadro John Dalton William Henry Jacques Charles Georg Simon Ohm Michael Faraday Coulomb 1735-1806 1736-1819 1737-1798 Guiseppe 1756-1856 1766-1844 1775-1836 1778-1850 1789-1854 1791-1867 B. P. Emile Germain Henri Hess Antonio Anastasio physician Clapeyron 1802-1850 q Volta, 1747-1827 1799-1864 Thomas Graham William Thompson Justus von Liebig Richard August James Joule Rudolph Clausius 1825-1898 James Maxwell Dmitri Mendeleev Johannes D. 1805-1869 Lord Kelvin, Francois-Marie Energy (1803-1873 Carl Emil (1818-1889) 1822-1888 1824-1907 Johann Balmer 1831-1879 1834-1907 Van der Waals Raoult Erlenmeyer 1837-1923 1830-1901 Consumed 1825-1909 Depends on Both work Thomas Martin Henri Louis Johannes Rydberg J. J. Thomson Heinrich R. Hertz, Max Planck Svante Arrehenius Walther Nernst Fritz Haber J. Willard Gibbs Lowry And heat Ludwig Boltzman LeChatlier 1854-1919 1856-1940 1857-1894 1858-1947 1859-1927 1864-1941 1868-1934 1874-1936 1839-1903 1844-1906 1850-1936 w Fitch Rule G3: Science is Referential ∆ EE=−final E initial =+ qw Johannes Nicolaus Niels Bohr Fritz London Wolfgang Pauli Werner Karl Linus Pauling Erwin Schodinger Friedrich H. Hund Gilbert Newton Lewis Bronsted Lawrence J. Henderson 1885-1962 Louis de Broglie 1900-1954 1900-1958 Heisenberg 1901-1994 1887-1961 1896-1997 1875-1946 1879-1947 1878-1942 (1892-1987) 1901-1976 1 Properties and Measurements To set a “heat flow” scale Property Unit Reference State Size m size of earth Volume cm3 m 1. Defined conditions: how experiment is performed Weight gram mass of 1 cm3 water at specified Temp open flask, closed flask, pressure (and Pressure) Temperature oC, K boiling, freezing of water (specified 2. Define the direction of heat flow by giving Pressure) a positive or negative number 1.66053873x10-24gamu (mass of 1C-12 atom)/12 quantity mole atomic mass of an element in grams Pressure atm, mm Hg earth’s atmosphere at sea level Energy, General Animal hp horse on tread mill heat BTU 1 lb water 1 oF calorie 1 g water 1 oC Kinetic J m, kg, s Electrostatic 1 electrical charge against 1 V Does the “system (earth)” gain energy? electronic states in atom Energy of electron in vacuum + heat For image above Electronegativity F - heat? system (earth) gains heat Heat flow measurements Reference state? from surroundings (sun) To set a “heat flow” scale First Law of Thermodynamics: Energy is conserved 1. Defined conditions: how experiment is performed open flask, closed flask, pressure 2. Define the direction of heat flow by giving a positive or negative number We would get a different answer if we asked “Does the “system (sun)” gain energy?” No universal change in energy For this question: the Just a transfer of energy + heat system (sun) loses heat -heat? to the surroundings (earth) 2 To set a “heat flow” scale surroundings 1. Defined conditions: how experiment is performed open flask, closed flask, pressure system 2. Define the direction of heat flow (q) by giving a positive or negative number q is + when heat flows into the system from the surroundings q is - when heat flows out of the system into the surroundings q =? 3. Chemical process in the “system” is defined by heat flow q>0 system q<0 system E = constant when System AND surroundings considered! endothermic q>0 exothermic q<0 ++2 Properties and Measurements Chemical reactions involve Zn() s+→2 H ( aq ) Zn ( aq ) + H2 ( g ) Property Unit Reference State 1. heat exchange Size m size of earth Volume cm3 m 3 As a review: Weight gram mass of 1 cm water at specified Temp Heat exchange (and Pressure) Constant Temperature oC, K boiling, freezing of water (specified At constant Atm.pressure who is oxidized? Pressure) Pressure who is reduced? -24 1.66053873x10 gamu (mass of 1C-12 atom)/12 what is the oxidation number on H ? quantity mole atomic mass of an element in grams 2 Pressure atm, mm Hg earth’s atmosphere at sea level Who is an oxidizing agent? Energy: Thermal BTU 1 lb water 1 oF calorie 1 g water 1 oC H = Greek: thalpein – to heat Kinetic J 2kg mass moving at 1m/s enthalpy en -in Energy, of electrons energy of electron in a vacuum H for (?) heat Electronegativity F Heat Flow into system = + qH= ∆ P 1 atm pressure = constant pressure Subscript Reminds us that This means heat flow, q, is enthalpy change Pressure is constant 3 ++2 Chemical reactions involve Zn() s+→2 H ( aq ) Zn ( aq ) + H ( g ) 2 ∆ EE= final− E initial = qw+ 1. heat exchange 2. work This is a form of Rule G3 ∆ EqPP=+(− PV∆ ) Science is referential Pressure- ∆ EHPVP =+∆ (− ∆ ) Generally final - initial Volume constant Atm. pressure ∆ EHPV=−∆ ∆ work P ∆ V w = − P∆ V Change in volume is typically small for Most reactions ∆ EHP ≈ ∆ This means we can measure the energy change of A chemical reaction by measuring the heat exchange At constant pressure 3 to 8 standard cubic feet of five Navy Avengers biogas per pound of manure. disappeared in the Bermuda The biogas usually contains 60 Triangle on Dec. 5, 194 to 70% methane. Methane First example problem will involve methane Gas We will prove to ourselves that the Pressure-Volume work is a Recovery Small contribution to the total energy change At landfills 4 Consider the contribution of volume of gas phase molecules Consider the contribution of volume change for water in this reaction CH42()gg+→22 O () CO 2 () g+ H 2 O () l CH42()gg+ 22 O ()→ CO 2 () g+ H 2 O () l PVnRT= 3 At constant T: ⎡ 18g ⎤ ⎡ 1cm water ⎤ ⎡ 1L ⎤ []2moleH2 O()l **⎢ ⎥ ⎢ ⎥ *⎢ 33⎥ = 0 . 036L PV()()∆∆= nRT ⎣ mol ⎦ ⎣ 1gwater ⎦ ⎣ 10 cm ⎦ PV()∆= n − n RT %&$*! Conversions – if ()gas final gas initial Interested see next slide 01013. kJ PV= [][]1 atm 0. 036 L = 0. 0036kJ ⎛ Latm⋅ ⎞ Latm− PV()(∆=−1 3 moles )⎜ 0. 0821⎟ 298K ⎝ mol⋅ K ⎠ Energy in kJ Most reactions total (q): ~ 1000 kJ By the end of %&$*! Conversions – if This module PV()∆=−48. 9316 Latm ⋅ Interested see slide after next PV 1 mole gas ~ 2.5 kJ We will see this Is “true” ⎛ 01013. kJ ⎞ PV 2mole liquid water ~ 0.0036 kJ PV()(∆=−48. 9316 Latm ⋅ )⎜ ⎟ =−49. kJ ⎝ Latm⋅ ⎠ 2mole change Sig fig tells us that PV energy small compared to q Optional Slide: conversion To set a “heat flow” scale 1. Defined conditions: how experiment is performed Constant Pressure 2. But not on the path taken (state property) ⎛ ⎞ ⎛ ⎛ kg ⎞ ⎞ Heat flow 5 ⎜ ⎟ ⎛ 101325. xPa 105 ⎞ ⎜ ⎜ 2 ⎟ ⎟ 33 3 ⎛ 101325. xPa 10 ⎞ ⎝ ms⋅ ⎠ ⎛ 10cm ⎞ ⎛ 1m ⎞ ⎜ J ⎟ ⎛ kJ ⎞ ()atm ⎜ ⎟ ⎜ ⎟ ()L ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ = 0101325. kJ depends ()atm ⎜⎝ atm ⎟⎠ ()L ⎜ ⎟ ⎜ 2 ⎟ ⎜ 2 ⎟ 3 ⎝ atm ⎠ ⎜ Pa ⎟ ⎝ L ⎠ ⎝ 10 cm⎠ ⎛ kg⋅ m ⎞ ⎝ 10 J ⎠ ⎜ ⎟ the conditions ⎜ ⎟ ⎜ ⎜ 2 ⎟ ⎟ ⎝ ⎠ ⎝ ⎝ s ⎠ ⎠ ⎧ ⎫ ⎛ ⎛ kg ⎞ ⎞ ⎛ ⎞ ⎜ ⎟ ⎪ 5 ⎜ ⎜ 2 ⎟ ⎟ 33 3 ⎪ 0101325..kJ ⎪⎛ 101325xPa 10⎞ ⎝ ms⋅ ⎠ ⎛ 10cm ⎞ ⎛ 1m ⎞ ⎜ J ⎟ ⎛ kJ ⎞ ⎪ = ⎜ ⎟ ⎨⎜ ⎟ ⎜ ⎟ ⎜ 2 ⎟ ⎜ 2 ⎟ ⎜ 3 ⎟ ⎬ ()()atm L ⎝ atm ⎠ ⎜ Pa ⎟ ⎝ L ⎠ ⎝ 10cm⎠ ⎛ kg⋅ m ⎞ ⎝ 10 J ⎠ ⎪ ⎜ ⎟ ⎪ H= enthalpy ⎜ ⎟ ⎜ ⎜ 2 ⎟ ⎟ ⎪ ⎝ ⎠ ⎝ s ⎠ ⎪ ⎩ ⎝ ⎠ ⎭ qHHH==∆ − reaction constan tpressure products reactan ts 5 Enthalpy is a state property (measured under constant pressure, but how measured under that Enthalpy is an “extensive” property constant pressure is not important) qH=>∆ 0 endothermic Depends upon the amount present HHproducts> reactan ts CH42()gg+→2 O () CO 2 () g+ 2 H 2 O () l ∆ H= − 890 kJ Think of heat as a reactant 890kJ of heat is released when 1 mole of methane H22 O()s +⎯→ heat⎯ H O Reacts with oxygen q =<∆ H 0 − 890kJ exothermic 1moleCH4()g HHproducts< reactan tss ⎛ − 890kJ ⎞ ⎜ ⎟ 2moleCH=− 1780 kJ CH42()gg+→2 O () CO 22 () g + H O () l + heat Think of heat as a product ⎜ ⎟ ()4()g ⎝ 1moleCH4()g ⎠ Properties and Measurements Context for the next example problem Property Unit Reference State 2006 Sept Sci. Am: World Wide Petroleum Usage Size m size of earth Land People Transport 3 Non- Volume cm m 29% of total use Weight gram mass of 1 cm3 water at specified Temp transportation (and Pressure) o Temperature C, K boiling, freezing of water (specified Total transportation Pressure) -24 =53% 1.66053873x10 gamu (mass of 1C-12 atom)/12 Land Freight 19% quantity mole atomic mass of an element in grams Pressure atm, mm Hg earth’s atmosphere at sea level Air People and Freight 5% Energy, General Animal hp horse on tread mill U.S. differs from world in distribution of petroleum use heat BTU 1 lb water 1 oF calorie 1 g water 1 oC 3 Non-transportation Kinetic J m, kg, s Transportation = 71.8% Electrostatic 1 electrical charge against 1 V electronic states in atom Energy of electron in vacuum 57.8% of Transportation= Electronegativity F Personal land transport Heat flow measurements constant pressure, define system vs surroundin = 41.5% of total U.S.