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 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 = kP A a P B b

Write Rate Expressions for: H 2(g) + N 2(g) NH 3(g) HCl (aq) + Ba(OH) 2(aq) BaCl 2(aq) + H 2 O (l)

Write Rate Expressions for: H 2(g) + N 2(g) NH 3(g) Rate = k(P H2 ) 3 (P N2 )

Write Rate Expressions for: 2HCl (aq) + 1Ba(OH) 2(aq) 1BaCl 2(aq) + 2H 2 O (l) Rate = k[HCl] 2 [Ba(OH) 2 ]

Write Rate Expressions for: 1 Cl 2(g) + 1 HOOH (aq) 2 HOCl (aq)

Write Rate Expressions for: 1 Cl 2(g) + 1 HOOH (aq) 2 HOCl (aq) Rate = k(P Cl2 ) or Rate = k[HOOH]

Write the Rate Law for: 2A (aq) + B (aq) + 3C (s) Products

Write the Rate Law for: 2A (aq) + B (aq) + 3C (s) P Rate = k[A] 2 [B]

Reaction Order The total number of reactants (coefficients) Equals total exponents in rate expression

Drill: Write the rate expression & determine rxn order for: SO 2(g) + O 2 (g) SO 3(g)

Drill: Write the rate expression & determine rxn order for: 2 SO 2(g) + 1 O 2 (g) 2 SO 3(g) Rate = k(P SO2 ) 2 (P O2 )

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

Experimental Results Exp [A] [B] Rate

Write the rate expression for: aA + bB + cC Products All aqueous

Experimental Results Exp # [A] [B] [C] Rate

Experimental Results Exp # [A] [B] [C] Rate

Solve All: Exp Data: Exp # [R] [S] [T] Rate 1) ) ) )

Solve All: Exp Data: Exp # [R] [S] [T] Rate 1) ) ) )

Drill: Solve All Exp Data: Exp # [R] [S] Rate 1) ) )

Solve All: Exp Data: Exp # [R] [S] Rate 1) ) )

Solving exponents with a calculator. A x = B

Log A x = log B xLog A = log B Thus:

x = Log B Log A

Clausius-Claperon Eq E a = R ln (T 2 )(T 1 ) k 2 (T 2 – T 1 ) k 1

Calculate the activation energy of a reaction whose rate constant is 2.0 x 10 3 at 27 o C and is 2.0 x 10 6 at 77 o C:

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 OrderRate Exp 0Rate = k 1 Rate = k[A] 2 Rate = k[A] 2

1st Order Age Dating Formula t = ln(A i /A f )t 1/

Reaction Mechanism The sequence of steps that make up the reaction process

Reaction Mechanism Step 1A  Bfast Step 2B  Cslow Step 3C  Dfast Total A  D

Reaction Mechanism The rate determining step in a reaction mechanism is the slowest step

Reaction Mechanism To solve the rate expression, you must use the slowest step

Solve Rate Expression A + B C + D fast 2C + A G fast 2D + B K fast 2G + 2K Prod. slow

Solve Rate Expression X + Y M + N fast M + N 2G slow 2N + G K fast 2G + 2K Prod. fast

Solve All: Exp Data Exp # T [A] [B] Rate 1) 27 o C ) 27 o C ) 27 o C ) 77 o C

Solving Rxn Exponent Rate 2 k [IO 3 - ] x [S 2 O 5 -2 ] y M/31 s k(0.10M) x (0.10M) y M/66 s k(0.10M) x (0.05M) y = =

[Z] Abs

Drill: Solve Rate Expr: X + Y M + N fast 3M + N 2G fast 2N K fast 2G + K Prod. slow

Rate Law & Net Rxn A + B C + Dfast 4C + A 2Gfast 4D + B 2Kfast G + K Q + Wslow Q + 2 WProd.fast

Review

Drill: Determine All Exp # T [A] [B] Rate 1) 27 o C ) 27 o C ) 27 o C ) 77 o C

Solve Rate Expression A + B C + Dfast 4 C + A 2Gfast 2 K 4D + B fast G + K Q + Wfast 2Q + 2W Prod.slow