Chem 161-2011 Lecture 17, Chapter 10

# Chem 161-2011 Lecture 17, Chapter 10 - CHEMISTRY 161-2011...

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Chem 161-2011 Lecture 17 1 CHEMISTRY 161-2011 LECTURE 17 CHAPTER 10 ENERGY CHANGES IN CHEMICAL REACTION ANNOUNCEMENTS E-MAIL EXAMS

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Chem 161-2011 Lecture 17 2 Today’s topics Chapter 10: 10.1 Energy and energy changes 10.2 Introduction to thermodynamics States and state functions The first law of thermodynamics W o r k a n d h e a t 10.3 Enthalpy Reactions carried out at constant volume or at constant pressure Enthalpy and enthalpy changes Thermochemical equations 10.4 Calorimetry Specific heat and heat capacity Constant-pressure calorimetry Constant-volume calorimetry
Chem 161-2011 Lecture 17 3 CHAPTER 10 RELEVANT EQUATIONS E = Δ U = q + w 1 Latm = 101.3 J Pressure-volume work: w = -P Δ V; therefore, E = q –P V Non-pressure-volume work: w = F x d (note, using a piston and cylinder, the piston has to move); F = m x a; w = m x a x d = m x g x d Units of non-pressure-volume work: m in kg, g = 9.81 m x s -2 , d in m; Units: kg x ms -2 x m = kgm 2 s -2 = J Heat Capacity = C = q/ Δ T molar heat capacity = C/mol = q/( Δ T x mol) Specific Heat Capacity = SHC = SH = C/g = (q/ Δ T)/g = q/ Δ Tg q = SHC x Δ T x g SHC H2O = 4.18J/g o C First law of thermodynamics: Energy is neither created nor destroyed. Therefore, heat lost by one = the heat gained by other. -q 1 = +q 2 Hess’s Law : Δ H is a state function, so path not important. Rules for changing enthalpy equations: o If the enthalpy equation is reversed, sign of Δ H is reversed. o If the enthalpy equation is halved, quantity of Δ H is halved. o If the enthalpy equation is doubled, quantity of Δ H is doubled. Enthalpy of Formation (more correctly, “Standard enthalpy of formation”) = Δ H o f o is for formation of one mole of product o from its elements o all reactants (i.e., elements) and products in their standard states (1 atm & 298K) o all elements in their most stable form, e.g., oxygen = O 2(g) ; mercury = Hg (l) ; s o d i u m = N a (s) o Δ H o f of elements = 0 Enthalpy of reaction : o Δ H o Rx = n p Δ H o f,products - n r Δ H o f,reactants

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Chem 161-2011 Lecture 17 4 Open system Closed system Isolated system
Chem 161-2011 Lecture 17 5 Another vibration Kinetic energy consists of three types of molecular motion

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Chem 161-2011 Lecture 17 6 System absorbs heat, q = + System is compressed, w = + (In this case, the system absorbs heat, but expands.)
Chem 161-2011 Lecture 17 7 TERMINOLOGY Thermochemistry: The study of the relationship between energy and chemical reactions. System: That part of the universe we are studying (e.g., a gas in a cylinder)

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## This note was uploaded on 02/20/2012 for the course 160 161 taught by Professor Kim during the Fall '08 term at Rutgers.

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Chem 161-2011 Lecture 17, Chapter 10 - CHEMISTRY 161-2011...

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