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Rates of Reaction and Chemical Equilibrium

Rates of Reaction and Chemical Equilibrium. 14.1 THE STUDENT WILL relate rates of reactions to kinetic Theory. [P.12.A.5]. Collision Theory – the set of assumptions regarding collisions and reactions Assumption 1 – Particles (atoms, molecules, or ions) must collide

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Rates of Reaction and Chemical Equilibrium

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  1. Rates of Reaction and Chemical Equilibrium

  2. 14.1 THE STUDENT WILL relate rates of reactions to kinetic Theory. [P.12.A.5] • Collision Theory – the set of assumptions regarding collisions and reactions • Assumption 1 – Particles (atoms, molecules, or ions) must collide • Assumption 2 – the orientation of the collision between particles must be favorable

  3. 14.1 THE STUDENT WILL relate rates of reactions to kinetic Theory. [P.12.A.5] • Assumption 3 – the collisions must have sufficient energy for a reaction to occur • Effective Collisions –Ones that have a favorable orientation and strikes with enough energy to cause a reaction.

  4. 14.2 THE STUDENT WILL EVALUATE FACTORS THAT INFLUENCE THE RATE OF REACTION including surface area, temperature, agitation, nature of reactants, and concentration. [P.12.A.5] • Rate Influencing Factors • 1. Nature of the reactants • 2. Surface Area • In heterogeneous reactions (involves reactants in more than one phase), one reactant can only react with the surface of a solid. The surface must be reacted exposing deeper particles within the solid. Grinding a solid will increase exposed surface area.

  5. 14.2 THE STUDENT WILL EVALUATE FACTORS THAT INFLUENCE THE RATE OF REACTION including surface area, temperature, agitation, nature of reactants, and concentration. [P.12.A.5] • A single cube measuring 1m3 has a surface area of 60,000cm2 • One side of the cube is 1m x 1m, or 100 cm x 100 cm. This is 10,000cm2 • There are six sides to a cube so the total area is 6 x 10,000cm2 = 60,000cm2

  6. 14.2 THE STUDENT WILL EVALUATE FACTORS THAT INFLUENCE THE RATE OF REACTION including surface area, temperature, agitation, nature of reactants, and concentration. [P.12.A.5] • Break this cube into single cubes of one cm3 will give you 6 million cm2 • A cube of 1m x 1m x 1m will also measure 100cm x 100cm x 100cm, or 1,000,000 cm3 • One cube measuring 1cm3 has a side that measures 1cm x 1cm, or 1cm2 • There are 6 side so 6 x 1cm2 is 6cm2. 6cm2 x 1,000,000 cubes is 6,000,000 cm2

  7. 14.2 THE STUDENT WILL EVALUATE FACTORS THAT INFLUENCE THE RATE OF REACTION including surface area, temperature, agitation, nature of reactants, and concentration. [P.12.A.5] • 3. Temperature • An increase in temperature increases the rate and energy of collisions due to an increase in kinetic energy • Since collisions happen more often and with greater force, the chances of an effective collision are greater

  8. 14.2 THE STUDENT WILL EVALUATE FACTORS THAT INFLUENCE THE RATE OF REACTION including surface area, temperature, agitation, nature of reactants, and concentration. [P.12.A.5] • 4. Concentration • An increase in concentration means more particles are in the same volume of space. • This means that the particles are closer together so they will collide more often, increasing the chance of an effective collision.

  9. 14.3 The student will interpret energy diagrams and explain the role of a catalyst in increasing reaction rate. [N.12.A.5, P.12.A.5, P.12.A.6] • 5. Agitation (stirring) • Stirring increases the kinetic energy in the particles knocking them into each other more often and more vigorously

  10. 14.3 The student will interpret energy diagrams and explain the role of a catalyst in increasing reaction rate. [N.12.A.5, P.12.A.5, P.12.A.6] • 6. Presence of a Catalyst • Activation Energy – the minimum amount of energy required to initiate a reaction • Catalyst – a chemical that reduces the amount of activation energy required to initiate a reaction; thus, speeding up the reaction.

  11. 14.3 The student will interpret energy diagrams and explain the role of a catalyst in increasing reaction rate. [N.12.A.5, P.12.A.5, P.12.A.6]

  12. 16.1 describe CHEMICAL EQUILIBRIUM qualitatively and quantitatively. [P.12.A.5] • Reversible Reactions – A reaction in which the products can regenerate the original reactants • N2O4 (colorless) ↔ 2NO2 (brown)

  13. 16.1 describe CHEMICAL EQUILIBRIUM qualitatively and quantitatively. [P.12.A.5] • Chemical equilibrium – The state in which the concentrations of reactants and products remain constant with time because the rate at which they are formed in each reaction equals the rate at which they are consumed in the opposite reaction

  14. 16.1 describe CHEMICAL EQUILIBRIUM qualitatively and quantitatively. [P.12.A.5] • aA + bB↔cC + dD • 1. a, b, c, d are the coefficients • 2. A,B, C, D are the substances • 3. [ ] means molar concentration

  15. 16.1 describe CHEMICAL EQUILIBRIUM qualitatively and quantitatively. [P.12.A.5] • Equilibrium Constant –Keq • 1. Keqis equal to the ratio of the product concentrations of the forward reaction (raised to powers indicated by their coefficients) to the reactant concentrations of the forward reactions (raised to powers indicated by their coefficients)

  16. 16.1 describe CHEMICAL EQUILIBRIUM qualitatively and quantitatively. [P.12.A.5] • 2. For a given reaction, the ratio of products to reactants is always the same regardless of initial concentration at constant temperature • 3. When reactant and product concentration are measured at equilibrium and plugged into the equation, the result is a constant (at a given temperature)

  17. 16.1 describe CHEMICAL EQUILIBRIUM qualitatively and quantitatively. [P.12.A.5] • The Law of Chemical Equilibrium – Every reversible reaction proceeds to an equilibrium state that has a specific ratio of the concentrations of products to reactants

  18. 16.2 WRITE AN EQUILIBRIUM (MASS ACTION) EXPRESSION FROM THE BALANCED REACTION EQUATION. [P.12.A.5]

  19. 16.2 WRITE AN EQUILIBRIUM (MASS ACTION) EXPRESSION FROM THE BALANCED REACTION EQUATION. [P.12.A.5] • Practice: • What is the equilibrium expression for 2CO (g) + O2 (g)↔2CO2 (g)

  20. 16.2 WRITE AN EQUILIBRIUM (MASS ACTION) EXPRESSION FROM THE BALANCED REACTION EQUATION. [P.12.A.5] • Practice: • Write the equilibrium expression for the reaction 2SO2 (g) + O2 (g)↔2SO3 (g)

  21. 16.2 WRITE AN EQUILIBRIUM (MASS ACTION) EXPRESSION FROM THE BALANCED REACTION EQUATION. [P.12.A.5] • Practice: • Write the equilibrium expression for the reaction CO(g)+ 3H2(g)↔CH4(g)+ H2O(g)

  22. 16.4 INTERPRET THE COMPLETENESS OF A REACTION BASED ON THE VALUE OF the equilibrium constant (K). [P.12.A.5] • Equilibrium Constant -Keq – A measure of the extent to which a reaction proceeds to completion • A. An equilibrium constant greater than 1 says that Keq“lies to the right” or “There is a greater concentration of products than reactants.

  23. 16.4 INTERPRET THE COMPLETENESS OF A REACTION BASED ON THE VALUE OF the equilibrium constant (K). [P.12.A.5] • B. An equilibrium constant of about 1 means that the product and reactant concentrations are both sizeable and near equal • C. An equilibrium constant less than 1 says that Keq“lies to the left” or “There is a greater concentration of reactants than products

  24. 16.4 INTERPRET THE COMPLETENESS OF A REACTION BASED ON THE VALUE OF the equilibrium constant (K). [P.12.A.5] • Numerator Larger than Denominator • A. > Greater than 1 • B. >> significantly greater than 1 • C. Equilibrium product concentration is greater than the equilibrium reactant concentration

  25. 16.4 INTERPRET THE COMPLETENESS OF A REACTION BASED ON THE VALUE OF the equilibrium constant (K). [P.12.A.5] • Numerator Smaller than Denominator • A. < Less than 1 • B. << Significantly less than 1 • C. Equilibrium reactant concentration is greater than the equilibrium product concentration

  26. 16.4 INTERPRET THE COMPLETENESS OF A REACTION BASED ON THE VALUE OF the equilibrium constant (K). [P.12.A.5] • Homogeneous equilibrium – Equilibrium conditions for reactions where all the reactants and products are in the same physical state

  27. 16.4 INTERPRET THE COMPLETENESS OF A REACTION BASED ON THE VALUE OF the equilibrium constant (K). [P.12.A.5] • Heterogeneous Equilibrium – Equilibrium conditions for reactions that involve substances in more than 1 physical state • A. The concentrations of pure solids and pure liquids are left out of the equilibrium equation

  28. 16.4 INTERPRET THE COMPLETENESS OF A REACTION BASED ON THE VALUE OF the equilibrium constant (K). [P.12.A.5] • Example: NH4Cl (s)↔ NH3(g) + HCl(g) • Keq = [NH3][HCl] • Write the equilibrium expression for the reaction C(s) + H2O(g)↔CO(g)+ H2(g)

  29. 16.4 INTERPRET THE COMPLETENESS OF A REACTION BASED ON THE VALUE OF the equilibrium constant (K). [P.12.A.5] • Write the equilibrium expression for the reaction NH4NO3(s)↔N2O (g) + 2H2O(g) • Keq = [N2O][H2O]2 • Write the equilibrium expression for the reaction ZnCO3(s)↔ZnO(s) + CO2 (g) • Keq= [CO2]

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