Please Pick Up  Chemical Reactions Problem Set.

Thermochemistry First Law of Thermodynamics Edward A. Mottel Department of Chemistry Rose-Hulman Institute of Technology

6/14/2015 Chemical Thermodynamics  Reading assignment: Chang: Chapter  A study of the energy changes which accompany the physical and chemical changes of matter.  Balanced chemical equations are used to describe changes in both physical state and molecular structure.

6/14/2015 A Thermodynamic Term Enthalpy The total heat energy content of a molecule. If a chemical process requires heat, the enthalpy change is endothermic. If a chemical process releases heat, the reaction change is exothermic.

6/14/2015 Chemical Reactions  Requires knowledge of the chemical nature of the reactants and products. Formula, phase, solubility, ionic character. Equations corresponding to these processes should be balanced and completely annotated (g, l, s, aq).

6/14/2015 Solution Reactions Endothermic and Exothermic NH 4 + (aq) + NO 3 – (aq)  H soln = kJ  mol –1 2 H + (aq) + SO 4 2– (aq)  H soln = kJ  mol –1 exothermic NH 4 NO 3 (s) H2OH2O H 2 SO 4 (conc) H2OH2O enthalpy of solution endothermic

6/14/2015 Changes in Physical State Reactions should be balanced and annotated Enthalpy of vaporization of water Enthalpy of sublimation of water Enthalpy of fusion of water H 2 O(g) H 2 O( l ) H 2 O(g)H 2 O(s) H 2 O (l) H 2 O(s)

6/14/2015 Chemical Reactions Examples Decomposition Single replacement Double replacement Cr 2 O 3 (s) + N 2 (g) + 4 H 2 O(g)(NH 4 ) 2 Cr 2 O 7 (s) 2 NaCl(aq) + I 2 (aq)2 NaI(aq) + Cl 2 (g) NaCl(aq) + H 2 CO 3 (aq)HCl(aq) + NaHCO 3 (s)

6/14/2015 Chemical Reactions Combustion and Formation Combustion Formation 2 CO 2 (g) + 3 H 2 O(g) C 2 H 5 OH (l) + 3 O 2 (g) Na 2 CO 3 (s)2 Na(s) + C(gr) + 3/2 O 2 (g) carbon is converted to hydrogen is converted to most common elemental form

6/14/2015 Combustion of sucrose (C 12 H 22 O 11 ) Formation of sucrose 12 CO 2 (g) + 11 H 2 O(g)C 12 H 22 O 11 (s) + 12 O 2 (g) C 12 H 22 O 11 (s)12 C(gr) + 11 H 2 (g) + 11/2 O 2 (g) Write the equation for each of the following processes more examples

6/14/2015 Combustion and Formation Write the equation for each of the following processes Combustion of iron(II) sulfide to form sulfur dioxide Formation of nickel(II) nitrate SO 2 (g) + FeO(s)FeS(s) + 3/2 O 2 (g) Ni(NO 3 ) 2 (s)Ni(s) + N 2 (g) + 3 O 2 (g)

6/14/2015 Thermodynamic Terms  Heat, q.  Work, w.  Internal energy, E or U  System  Surroundings  Enthalpy, H  State Functions

6/14/2015 Thermal Energy q What is the difference between heat and temperature? Are heat and temperature intensive or extensive properties?properties Heat flows form a warmer body to a cooler body.

6/14/2015 Thermal Energy q Intensive properties are independent of amount. Are heat and temperature intensive or extensive properties? Heat flows form a warmer body to a cooler body.

6/14/2015 Work F d Work has an intensive and a capacitive factor. What is the difference between work and being tired?

Work Type of Work mechanical expansion electrical Intensity force pressure potential difference Capacity distance volume change (dV) amount of electricity (charge) gravitationalgravityheight x mass

6/14/2015 Internal Energy  E or U  The total kinetic and potential energy of a molecule or ion Molecular motion Electronic changes

6/14/2015 Molecules Store Energy in Molecular Motion translation

6/14/2015 Electronic Changes endothermic change in electron energy levels O h O triplet oxygensinglet oxygen OHHO HH exothermic bond formation

6/14/2015 First Law of Thermodynamics  U = energy gained - energy lost The change in internal energy of a system is equal to the energy added to the system, minus the energy lost by the system.

25 ºC200 ºC400 ºC800 ºC  E = q + w First Law of Thermodynamics The change in internal energy is equal to the heat added and the work done on the system. What’s happening to the gas in the rigid bulb?

6/14/2015 Closed systemIsolated system q Surroundings - Everything else (the rest of the universe). System - any region of space or material which is considered in dealing with energy changes that matter undergoes. m m

6/14/2015  1.0 atm  1.1 atm  1.2 atm  1.3 atm  1.4 atm  1.5 atm  1.6 atm  1.7 atm  1.8 atm  2.0 atm  2.3 atm  2.7 atm  3.2 atm First Law of Thermodynamics  E = q + w  4.0 atm What’s happening to the temperature of the gas? Why?

6/14/2015 First Law of Thermodynamics  E = q + w Explain what is happening using the First Law of Thermodynamics.  1.0 atm

6/14/2015 Internal Energy translation The total energy (E or U) of a molecule or ion is due to all sources of kinetic and potential energy.

6/14/2015 Internal Energy  The total energy (E or U) of a molecule or ion is due to all sources of kinetic and potential energy translation

6/14/2015 Work FFFFFFFFFFFFFFFFFFFFFFFF w = F·d d Work has an intensive and a capacitive factor. What is the difference between work and being tired?

6/14/2015 Molecules Store Energy in Molecular Motion translation