Bell Ringer May 11th

Bell Ringer May 11th

Bell Ringer 11th May The law of conservation of energy: energy cannot be ________ or _______. It can only be ________ or __________. Transfer of energy always takes place from a substance at a _______ temperature to a substance at a _______ temperature Three methods of heat energy transfer: _______ , __________, and __________. 1 Thermochemical Equations 2 Thermochemical Equations A Thermochemical Equation is a balanced stoichiometric chemical equation that includes the enthalpy change, H.H.

Enthalpy (H) is the transfer of energy in a reaction (for chemical reactions it is in the form of heat) and H.H is the change in enthalpy. By definition, H.H = Hproducts Hreactants Hproducts < Hreactants, H.H is negative Hproducts > Hreactants, H.H is positive 3 Thermochemical & Endothermic/ Exothermic equations Depending on the sign of H.H, the reaction can either be exothermic or endothermic. Exothermic reactions release heat from the system to the surroundings so the temperature will rise. H.H will be negative because the reaction loses heat. Endothermic reactions absorb heat from the surroundings into the system so the temperature will decrease. H.H will be positive because the reaction absorbs heat.

4 Classify the following as endothermic or exothermic Ice melting Endothermic 2 C4H10(g) + 13 O2(g) 10 H2O(g) + 8 CO2(g) H.Hrx = -5506.2 kJ/mol Exothermic 2 HCl (g) + 184.6 kJ H2 (g) + Cl2 (g) Endothermic Water vapor condensing Exothermic 5 Exothermic vs. Endothermic EXOTHERMIC

ENDOTHERMIC A change in a chemical A change in chemical energy where energy/heat EXITS the chemical system Results in a decrease in chemical potential energy H is negativeH is negative energy where energy/heat ENTERS the chemical system Results in an increase in chemical potential energy H is negativeH is positive 6 Thermochemical equations using Standard Heat of Formations - Solving for change in H (H)H)H)

C2H2(g) + 2 H2(g) C2H6(g) Substance DHf (kJ/mol) C2H2(g) C2H6(g) 226.7 -84.7 Standard Heat of Formations = DHf Remember By definition, H.H = H products H reactants 7 Thermochemical equations using Standard Heat of Formations DHf Write the equation for the heat of formation Substance (kJ/mol)

of C2H6(g) C2H2(g) 226.7 1st: Using our balanced chemical C2H6(g) -84.7 equation, we see how many moles of each compound we have. C2H2(g) + 2 H2(g) C2H6(g) [(H2) does not have a DHf ] 1 mol of C2H2(g) and 1 mol C2H6(g) 2nd: We plug in the Hf for each of our compounds, remembering that H = [Hf products] [Hf reactants] rdH = [C2H6(g)] [C2H2(g)] = 3 : We solve for H H = [-84.7] [226.7] = -331.4 kJ/mol 8 Practice Problems

Substance Solve for the H.Hrx and write the following thermochemical equations. DHf (kJ/mol) CaCO3(s) -1207.6 CaO(s) -634.9 C 4H10 (g) -30.0 H2O (g) -241.82

CO2 (g) -393.5 1. What is the H.Hrx for the process used to make lime (CaO)? CaCO3(s) CaO(s) + CO2(g) 2. What is the H.Hrx for the combustion of C4H10(g)? 2 C4H10 (g) + 13 O2 (g) 10 H2O (g) + 8 CO2 (g) 9 Practice Problems Solve for the H.Hrx and write the following thermochemical equations. 1. What is the H.Hrx for the process used to make lime (CaO)? CaCO3(s) CaO(s) + CO2(g) Substance DHf (kJ/mol)

CaCO3(s) -1207.6 CaO(s) -634.9 C 4H10 (g) -30.0 H2O (g) -241.82 CO2 (g) -393.5 H.Hrx = [H.Hf (CaO) + H.Hf (CO2)] [H.Hf (CaCO3)] H.Hrx = [(-634.9)+(-393.5)] [(-1207.6)] H.Hrx = [ -1028.4] [-1207.6] = +179.2 kJ

CaCO3(s) CaO(s) + CO2(g) H.Hrx = 179.2 kJ/mol 10 Practice Problems Solve for the H.Hrx and write the following thermochemical equations. 2. What is the H.Hrx for the combustion of C4H10(g)? 2 C4H10 (g) + 13 O2 (g) 10 H2O (g) + 8 CO2 (g) H.Hrx = [H.Hf (H2O) + H.Hf (CO2)] [H.Hf (C4H10)] (We do not include O2 because its H.Hf is 0.) Substance DHf (kJ/mol) CaCO3(s) -1207.6

CaO(s) -634.9 C 4H10 (g) -30.0 H2O (g) -241.82 CO2 (g) -393.5 H.Hrx = [10(-241.82)+8(-393.5)] [2(-30.0)] H.Hrx = [ -5566.2] [-60.0] = -5506.2 kJ 2 C4H10 (g) + 13 O2 (g) 10 H2O (g) + 8 CO2 (g) H.Hrx = -5506.2 kJ/mol 11

Recently Viewed Presentations

  • Program for Autoimmune Disease Intervention (PADI)

    Program for Autoimmune Disease Intervention (PADI)

    Health Impact "Deliverables": A toolkit for a new approach to autoimmunity Program for Autoimmune Disease Intervention We anticipate that a successful result from this Program will be the widespread use of such profiling tools for early diagnosis, selection of therapy,...
  • Surveillance, Democracy and the State

    Surveillance, Democracy and the State

    (b) where an individual has been subjected to unauthorised surveillance (ALRC 2008) 2010 Victorian Law Reform Commission recommended a law and a set of guiding principles for the responsible use of surveillance devices in public places (VLRC 2010) Challenges Involved...
  • Metodo circuitale: componenti e leggi di Kirchhoff

    Metodo circuitale: componenti e leggi di Kirchhoff

    Metodo circuitale: componenti e leggi di Kirchhoff Capitolo 1 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *...
  • Energy Innovation under the Clean Development Mechanism

    Energy Innovation under the Clean Development Mechanism

    Composting of solid biomass waste separated from the Palm Oil Mill Effluent (POME) through the use of AVC Sludge Dewatering System at Lian Hup Palm Oil Mill (Owned by Harn Len Corporation Bhd., Palm Oil Mill Division) Thermal energy recovery...
  • Ecclesiastes Chapters 5-6 Part of the Wisdom Literature

    Ecclesiastes Chapters 5-6 Part of the Wisdom Literature

    Ecclesiastes Chapter 6. 1. Wealth consumed by a foreigner: (Ecc 6:1-2)1 There is . an evil . which I have seen under the sun, and it is common among men: 2 A man to whom God has given riches and...
  • EECS 498 Advanced Embedded Systems

    EECS 498 Advanced Embedded Systems

    3.2V for lithium iron phosphate and lithium nickel manganese cobalt gets to 3.7V (both with graphite negative electrode) As normal, has a capacity in mAh, but that capacity also describes the . ... Lead Acid. Electrolysis in flooded cells occurs...
  • Late Middle Ages (1300-1450)Chapter 15, Section 5

    Late Middle Ages (1300-1450)Chapter 15, Section 5

    -war between English & French (William the Conqueror, of Normandy, was king of England, so his descendants believed they had claim to France) (1337-1455) French defeated English hurt English economy & led to War of the Roses (civil war between...
  • Presentation for Directors

    Presentation for Directors

    Previously - Quality and Risk Profiles (QRPs) for acute hospitals. advanced statistical modelling. New model - Intelligent monitoring informs programme of inspections (Sept 2013) Clarity about indicators they will prioritise, rather than a model that claims to scan all information...