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Drill: Calculate the osmotic pressure of 5.0 g NaOH in 7500 mL soln at 27 o C. Drill: Calculate the heat change when 25.0 g of H 2 O goes from 66.3 o C to 26.3 o C. C water = 4.18 J/gK. Chemical Kinetics or Reaction Rates. Reaction Rate.
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Drill: Calculate the osmotic pressure of 5.0 g NaOH in 7500 mL soln at 27oC.
Drill: Calculate the heat change when 25.0 g of H2O goes from 66.3oC to 26.3oC.Cwater = 4.18 J/gK
Reaction Rate • The speed at which reactants become products in a chemical reaction • M/s = mole/Ls
Kinetic Theory • All matter is made up of tiny particles • The particles are in constant motion • All collisions are elastic ?
Elastic Collisions • Collisions in which there is no energy change
Particles Reacting • For particles to react, they must collide • Reaction rate is dependent on collision rate
Particles Reacting • When a reaction takes place, an energy change occurs • Collisions (in which reactions occur) are not elastic
Reaction Rate • Rate = - d[Reactant]/dt • Rate = +d[Product]/dt • M/s
Factors Affecting Rxn Rate • Concentration, Temperature, Agitation, Process, Orientation, Catalyst, SA of Solid, Pressure of Gas, Reaction Mechanism
Drill: List & describe at least 5 factors that will affect reaction rates
Rate Expression • An equation showing how rate depends on the number of reactants in a rate determining reaction
Rate Expression • Rxn: aA(aq) + bB(aq) • P • Expr: Rate = k[A]a[B]b • [A] = molarity of A
Rate Expression • Rxn: aA(g) + bB(g) • Product • Exp: Rate = kPAaPBb
Write Rate Expressions for: H2(g) + N2(g) NH3(g) HCl(aq) + Ba(OH)2(aq) BaCl2(aq) + H2O (l)
Write Rate Expressions for: H2(g) + N2(g) NH3(g) Rate = k(PH2)3(PN2)
Write Rate Expressions for: 2HCl(aq) + 1Ba(OH)2(aq) 1BaCl2(aq) + 2H2O (l) Rate = k[HCl]2[Ba(OH)2]
Write Rate Expressions for: 1 Cl2(g) + 1 HOOH (aq) 2 HOCl(aq)
Write Rate Expressions for: 1 Cl2(g) + 1 HOOH (aq) 2 HOCl(aq) Rate = k(PCl2) or Rate = k[HOOH]
Reaction Order • The total number of reactants (coefficients) • Equals total exponents in rate expression
Drill: Write the rate expression & determine rxn order for: SO2(g) + O2 (g) SO3(g)
Drill: Write the rate expression & determine rxn order for: 2 SO2(g) + 1 O2 (g) 2 SO3(g) Rate = k(PSO2)2(PO2)
Determining Rxn Order • Find rate expression ratios • (Ratio of concentrations)x = rate ratio • x = exponent
Write the rate expression for: aA + bB Products All aqueous
The next slide includes data from an experiment where various concentrations of A & B were added together, and the rates of product formation was measured.
Experimental Results Exp [A] [B] Rate 1 1.0 1.0 2 2 2.0 1.0 4 3 1.0 2.0 8
Experimental Results Exp [A] [B] Rate 1 1.0 1.0 2 2 2.0 1.0 4 3 1.0 2.0 8
Write the rate expression for: aA + bB + cC Products All aqueous
Experimental Results Exp # [A] [B] [C] Rate 1 0.1 0.1 0.1 3 2 0.3 0.1 0.1 81 3 0.1 0.3 0.1 27 4 0.1 0.1 0.3 3
Experimental Results Exp # [A] [B] [C] Rate 1 0.1 0.1 0.1 3 2 0.3 0.1 0.1 81 3 0.1 0.3 0.1 27 4 0.1 0.1 0.3 3
Solve All: Exp Data: Exp # [R] [S] [T] Rate 1) 0.25 0.20 0.10 2 2) 0.25 0.60 0.10 18 3) 0.50 0.20 0.10 4 4) 0.25 0.20 0.40 32
Solve All: Exp Data: Exp # [R] [S] [T] Rate 1) 0.25 0.20 0.10 2 2) 0.25 0.60 0.10 18 3) 0.50 0.20 0.10 4 4) 0.25 0.20 0.40 32
Drill: Solve AllExp Data: Exp # [R] [S] Rate 1) 0.25 0.20 2 2) 0.25 0.60 18 3) 0.50 0.20 4
Solve All: Exp Data: Exp # [R] [S] Rate 1) 0.25 0.20 2 2) 0.25 0.60 18 3) 0.50 0.20 4
Ax = B Log Ax = log B xLog A = log B Thus:
Log B Log A x =
Clausius-Claperon Eq (T2)(T1) k2 (T2 – T1) k1 Ea= R ln
Calculate the activation energy of a reaction whose rate constant is 2.0 x 103 at 27oC and is 2.0 x 106 at 77oC:
Drill: List & describe at least 5 factors that will affect reaction rates
Half-Life • The time required for one half of the reactants to change into products in a reaction
Useful Relationships Rxn Order Rate Exp 0 Rate = k 1 Rate = k[A] 2 Rate = k[A]2