1 / 16

Chapter 6 Chemical Reactions and Quantities

Chapter 6 Chemical Reactions and Quantities. 6.9 Energy Changes in Chemical Reactions. Reaction Conditions. Reaction conditions for a chemical reaction require collisions between reacting molecules collisions with sufficient energy to break the bonds in the reactants

zavad
Download Presentation

Chapter 6 Chemical Reactions and Quantities

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Chapter 6 Chemical Reactions and Quantities 6.9Energy Changes inChemical Reactions

  2. Reaction Conditions Reaction conditions for a chemical reaction require • collisions between reacting molecules • collisions with sufficient energy to break the bonds in the reactants • the breaking of bonds between atoms of the reactants • the forming of new bonds to give products

  3. Chemical Reactions In the reaction H2(g) + I2(g) 2HI(g), • the reactants H2 and I2 collide • the bonds of H2 and I2 break • the bonds for HI form H2 + I2 collision bonds break HI new bonds form

  4. Activation Energy Activation energy • is the minimum energy required upon collision for a reaction to take place

  5. Heat of Reaction The heat of reaction • is the amount of heat absorbed or released during a reaction • is the difference in the energy of the reactants and the products • Has the symbol ΔH ΔH = ΔHproducts − ΔHreactants

  6. Exothermic Reactions In an exothermic reaction, • the energy of the products is less than the energy of the reactants • heat of reaction is released • heat is a product C(s) + O2(g) CO2(g) + 394 kJ ΔH = –394 kJ/mole (heat released)

  7. Endothermic Reactions In an endothermic reaction, • heat is absorbed • the energy of the products is greater than the energy of the reactants • heat is a reactant N2(g) + O2(g) + 180 kJ 2NO(g) ΔH = 180 kJ (heat added)

  8. Summary Reaction Energy Heat Sign of Type Change in ReactionΔH Endothermic Heat absorbed Reactant side + Exothermic Heat released Product side –

  9. Learning Check Identify each of the following reactions as: EX) exothermic or EN) endothermic A. N2(g) + 3H2(g) 2NH3(g) + 22 kcal B. CaCO3(s) + 133 kcal CaO(s) + CO2(g) C. 2SO2(g) + O2(g) 2SO3(g) + heat

  10. Solution EX A. N2(g) + 3H2(g) 2NH3(g) +22 kcal EN B. CaCO3(s) +133 kcal CaO(s) + CO2(g) EX C. 2SO2(g) + O2(g) 2SO3(g) + heat

  11. Guide to Calculations Using Heat of Reaction ( H)

  12. Heat Calculations for Reactions In the reaction N2(g) + O2(g)2NO(g), ΔH = 180 kJ. If 15.0 g of NO are produced, how many kJ were absorbed? STEP 1Given: 15.0 g of NO produced ΔH = 180 kJ/2 moles of NO Need: kJ absorbed STEP 2 Plan: g of NO moles of NO kJ

  13. Heat Calculations for Reactions (continued) STEP 3 Write the conversion factors: 2 moles NO = 180 kJ 180 kJ and 2 moles NO 2 moles NO 180 kJ 1 mole NO = 30.0 g of NO 1 mole NO and 30.0 g NO 30.0 g NO 1 mole NO STEP 4 Set up the problem to calculate kJ: 15.0 g NO x 1 mole NO x 180 kJ = 45 kJ 30.0 g NO 2 moles NO

  14. Learning Check How many grams of O2 reacted if 306 kcal are released in the following reaction? CH4(g) + 2O2(g) CO2(g) + 2H2O(l) + 213 kcal 1) 91.9 g of O2 2) 46.0 g of O2 3) 2.87 g of O2

  15. Solution 1) 91.9 g of O2 STEP 1 Given: 306 kcal released ΔH = 213 kcal /2 moles of O2 Need: g of O2 reacted STEP 2 Plan: kcal moles of O2 g of O2 STEP 3 Write the conversion factors: 2 moles of O2 = 213 kcal 213 kcal and 2 moles O2 2 moles O2 213 kcal

  16. Solution (continued) STEP 3 (continued) 1 mole of O2 = 32.0 g of O2 32.0 g O2 and 1 mole O2 1 mole O2 32.0 g O2 STEP 4 Set up the problem to calculate g of O2: 306 kcal x 2 moles O2 x 32.0 g O2 = 91.9 g of O2 (1) 213 kcal 1 mole O2

More Related