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Topic: Kinetics & Equilibrium

Topic: Kinetics & Equilibrium. Aim: How do you determine if a reaction is endothermic or exothermic? DN: Explain why an increase in temperature increases the rate of a reaction. HW :. Endothermic/Exothermic. Endothermic – energy absorbed H reactants = 5 kJ, H products = 10 kJ

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Topic: Kinetics & Equilibrium

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  1. Topic: Kinetics & Equilibrium • Aim: How do you determine if a reaction is endothermic or exothermic? • DN: Explain why an increase in temperature increases the rate of a reaction. • HW:

  2. Endothermic/Exothermic • Endothermic – energy absorbed • Hreactants = 5 kJ, Hproducts = 10 kJ • ΔH = 10 – 5 = 5 kJ • In endothermic rxns, ΔH is POSITIVE • Exothermic – energy released • Hreactants = 10 kJ, Hproducts = 5 kJ • ΔH = 5 – 10 = -5 kJ • In exothermic rxns, ΔH is NEGATIVE

  3. Heat of Reaction • Substances have potential energy or heat content • Heat of Reaction – amt of heat given off or absorbed in a rxn. • Difference between energy of reactants & energy of products • ΔH (change in heat from beginning to end)

  4. Using Table I • Heats of Reaction at 101.3 kPa and 298 K • List of reactions • Shows if rxn is endo (+) or exo (–)

  5. Reading Table I

  6. Using Table I How much heat is needed to produce 2 moles of HI? • Thought Process: • Find reaction on Table I that produces HI. • How many moles of HI did that rxn yield? (Remember # of mol. = coefficient) • How much heat was required for the reaction? • +53kJ • How much heat is needed to produce 1 mole of HI? • Answer: 53/2 = 26.5kJ

  7. Using Table I Give the ΔH Value & tell if the rxn is endo or exo 1. CH4 + 2O2 CO2 + 2H2O 2. 2CH3OH + 3O2 2CO2 + 4H2O 3. N2(g) + O2(g)  2NO(g) - How much heat is needed to produce 2 moles of NO(g)? - How much heat is needed to produce 1 mole of NO(g)?

  8. Using Table I • Determining the Heat of Formation (Hf) • Heat of Formation -the amount of heat released or absorbed when one mole of a compound is produced from its elements • (- sign indicates exothermic reaction) • What is the Hfof NO ? • +91.3 • Why? 182.6/2

  9. Using Table I • Determining if a compound is stable. Compounds with a negative Heat of Reaction are stable (more negative = more stable) Which is more stable? NH3 (g) or H2O (g) H2O (g)(-483.6) NH3 (– 91.8)

  10. Using Table I How do you draw an energy diagram for a reaction using table I? • Draw the energy diagram for the reaction producing 2 NO2

  11. Thought Question • Draw an energy diagram for an endothermic reaction and indicate with a dashed line what it would look like if a catalyst were added

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