- Zero Order Example (start with 100 on overhead, eat 10 every 5 seconds)
- First Order Example (start with 100 on overhead, eat 1/5 every 5 seconds)
- Second Order Example (start with 100 on overhead, eat 0.006 of number squared)
- Experiment with General Graph to show effect of rate.Reaction Rate and Order

- Rates as [delta]C/[delta]t
- Overhead, and Figure 15.2 from Textbook
- Rate for specific product or reactant
- For the reaction 2 NO
_{2}<-> 2 NO + O_{2}At 300 C- Data from Zumdahl
**time****NO**_{2}**NO****O**_{2}0 0.0100 0 0 50 0.0079 0.0021 0.0011 100 0.0065 0.0035 0.0018 150 0.0055 0.0045 0.0023 200 0.0048 0.0052 0.0026 250 0.0043 0.0057 0.0029 300 0.0038 0.0062 0.0031 350 0.0034 0.0066 0.0033 400 0.0031 0.0069 0.0035 - Graph concentration vs time for NO
_{2} - Calculate concentration of other species and graph
- Calculate average rate
- from 0 to 50
- from 200 to 250

- Completed Spreadsheet
- Compare rates for each species

- CD-ROM 15-2 side bar (Bleach and dye)
- Surface Area. ( internet © Saunders, 1997)
- Concentration. CD-ROM, 15-4 (
internet © Saunders, 1997)
- Mg (
*s*) + 2 HCl (*aq*) -> H_{2}(*g*) + Mg^{2+}+ 2 Cl^{1-}(*aq*) - 2 N
_{2}O_{5}-> 4 NO_{2}+ O_{2}(Initial Rate vs concentration)

- Mg (

## The Rate Law: The Effect of Concentration on Reaction Rate

- The rate law
- Expression:

for a reaction: aA + bB -> cC + dD

rate is rate = k [A]^{x}[B]^{y}

- Expression:
- Discuss units for kinetics problems (Handout).
- Method of Initial Rates:
Determine rate law from initial rates or rates at different concentrations. (Lecture Problems).
- Derive Relationship
ln(Rate Where:_{1}/Rate_{2}) = x ln(A_{1}/A_{2})- Rate
_{1}is the rate under the first conditions. - Rate
_{2}is the rate under the second conditions. - A
_{1}is the concentration of A for the first conditions. - A
_{2}is the concentration of A for the second conditions. - x is the reaction order for A.

- Rate
- For the reaction:
NH _{4}^{+}(*aq*) + NO_{2}^{-}(*aq*) -> N_{2}(*g*) + 2 H_{2}O (*l*)With the following experimental data.

Experimental Data [NH _{41+] (M)}[NO _{2}^{1-}] (M)Rate (M s ^{-1}0.100 0.005 1.35*10 ^{-7}0.100 0.010 2.75*10 ^{-7}0.200 0.010 5.4*10 ^{-7}- Determine the order of a reaction
- Determine k for reaction:
- Write the rate law
- Use the rate law to calculate the rate for new concentrations.

## The Integrated Rate Law: The Dependence of Concentration on Time

(Lecture Problems)- Plot of concentration vs time, and rate vs time
- Units for axis
- Units for area under curve
- Integration of rate equation

- Derive 1
^{st}order integrated rate equation - Use the integrated rate equation to find the concentration at time
*t*for:C _{2}H_{5}Cl -> C_{2}H_{4}+ HCl at 700 K, k = 2.50*10^{-3}min^{-1}- If the initial concentration of C
_{2}H_{5}Cl is 3.45 atm, how long does it take for the partial pressure of C_{2}H_{5}Cl to drop to 1.00 atm? - What is the partial pressure of C
_{2}H_{5}Cl after six hours? - How long does it take for the C
_{2}H_{5}Cl concentration to drop to 1/2 the initial concentration? - How long does it take for 99% of the C
_{2}H_{5}Cl to react?

- If the initial concentration of C
- Graph Concentration vs time from integrated rate equation (overhead).

## Rate laws, integrated rate equation, and units

**Reaction Order****Rate****Rate Law****Integrated Rate Equation****Linear Plot****Slope****Units for***k***0**[delta] concentration

-----------------------

[delta] timerate = *k*[A] _{0}- [A]_{t}=*k*t[A] vs time -k concentration time ^{-1}

mol liter^{-1}sec^{-1}

pressure time^{-1}**1**[delta] concentration

-----------------------

[delta] timerate = *k*[A]ln ([A] _{t}/[A]_{0}) = -*k*tln [A] vs time - *k*sec ^{-1}**2**[delta] concentration

-----------------------

[delta] timerate = k [A] ^{2}

rate =*k*[A] [B](1/[A] _{t}) - (1/[A]_{0}) =*k*t(1/[A]) vs time k concentration ^{-1}time^{-1}

liter mole^{-1}sec^{-1}

pressure^{-1}time^{-1}## Graphing Kinetics Data

Graphing Kinetics Data (pdf)

## The Effect of Temperature on Reaction Rate

- Collision Theory
- Collision Energy NO + O
_{3}-> NO_{2}+ O_{2}( internet© Saunders, 1997) - Orentation NO + O
_{3}-> NO_{2}+ O_{2}( internet© Saunders, 1997) - Successful Reaction NO + O
_{3}-> NO_{2}+ O_{2}( internet© Saunders, 1997) - Energy Diagram (Overhead)
- Reaction Energy Diagram F
^{1-}+ CH_{3}Cl -> CH_{3}F + Cl^{1-}( internet© Saunders, 1997) - Temperature and reaction rate, bleach demo (
internet © Saunders, 1997)
- Concentration and reaction (collision) rate).

- Collision Energy NO + O
- The Arrhenius Equation
- Graphing ln(k) vs 1/T, idea of linear relationships
- Derive relationship
- Show graph on Lotus

- Calculations with the Arrhenius equiaton
- Given A and E
_{a}, determine k at T - Find change in rate at two T's from E
_{a} - Determine E
_{a}from k at two T's - Arrhenius Plot to find E
_{a}

- Given A and E
- (Lecture Problems)

## Reaction Mechanisms

## Catalysis

- H
_{2}O_{2}Decomposition ( internet© Saunders, 1997) - Catalysis reaction steps
- Given the reaction steps:
- NO + O
_{3}-> NO_{3}+ O (slow)

__NO___{3}+ O -> NO_{2}+ O_{2}(fast)NO + O

_{3}-> NO_{2}+ O_{2}(overall) - And an additional step:
- Combines as:
- Which species is a catalyst?
- Which species is an intermediate?
- How does this catalyst effect the rate of the reaction

NO_{2}+ O -> NO + O_{2}

NO + O_{3}-> NO_{2}+ O_{2}

__NO___{2}+ O -> NO + O_{2}O

_{3}+ O -> 2 O_{2} - Catalysis Energetics and Reaction Rates. (Lecture Problems)
For the ovrall reaction: O

_{3}+ O -> 2 O_{2}- For the catalyzed reaction E
_{a}= 11.9 kJ - For the uncatalyzed reaction E
_{a}= 14.0 kJ - Draw an energy level diagram
- What is the rate constant at 298 K for each mechanism?
- For the catalytic destruction of O
_{3}by Cl E_{a}= 2.1 kJ, what would this rate constant be at 298 K?

- For the catalyzed reaction E

This page is maintained by

Scott Van Bramer

Department of Chemistry

Widener University

Chester, PA 19013Please send any comments, corrections, or suggestions to svanbram@science.widener.edu.

This page has been accessed 350 times since 5/30/97.

Last Updated Friday, May 25, 2001 1:59:43 PM - Data from Zumdahl