Topic No. 3 -Chemical Kinetics Lecture
13/12/2011
Course Title: General and Inorganic Chemistry
TOPIC 3: CHEMICAL KINETICS
Lecturer and contacts Mr. Vincent Madadi Department of Chemistry, University of Nairobi P. O. Box 30197-00100, Nairobi, Kenya Chemistry Dept. Rm 114 Tel: 4446138 ext 2185 Email: vmadadi@uonbi.ac.ke, madadivin2002@yahoo.com Website: http://www.uonbi.ac.ke/staff/vmadadi
12/13/2011 mov 1
Introduction
• Kinetics is the study of rates of chemical reactions and the mechanisms by which they occur. • The reaction rate is the increase in concentration of a product per unit time or decrease in concentration of a reactant per unit time. • A reaction mechanism is the series of molecular steps by which a reaction occurs.
12/13/2011
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13/12/2011
Reaction rate
2 NO2(g) → 2 NO(g) + O2(g)
12/13/2011
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Thermodynamic vs kinetics of reaction
• Thermodynamics determines if a reaction can occur. Kinetics determines how quickly a reaction occurs • Some reactions that are thermodynamically feasible are kinetically so slow as to be imperceptible • The Rate of a Reaction Cdiamond + O2(g)→ CO2(g) ΔG°= -396kJ Very Slow H+(aq) + OH-(aq) → H2O(l) ΔG°= -79kJ 12/13/2011 Very Fastmov
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13/12/2011
Rate of chemical reaction
• 2 N2O5 → 4 NO2 + O2 • 2 moles of N2O5 disappear for every 4 moles of NO2 and 1 mole of O2 formed. • Reaction rates are the rates at which reactants disappear or products appear.
12/13/2011
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Reaction rate
• Reaction rate is the change of concentration of a reactant or product per unit time aA + bB → cC + Dd Reaction rate = ΔConcentration Δtime
• Rate is expressed either as rate of appearance of product or rate of disappearance of reactant • E.g. aA + bB → cC + dD
12/13/2011 mov 6
3
13/12/2011
Reaction rate
• Mathematically, the rate of a reaction can be written as:
•
Square brackets [ ] are often used to express molarity (i.e.[HCl] means Molarity of HCl) The relative rates of consumption of
Course Title: General and Inorganic Chemistry
TOPIC 3: CHEMICAL KINETICS
Lecturer and contacts Mr. Vincent Madadi Department of Chemistry, University of Nairobi P. O. Box 30197-00100, Nairobi, Kenya Chemistry Dept. Rm 114 Tel: 4446138 ext 2185 Email: vmadadi@uonbi.ac.ke, madadivin2002@yahoo.com Website: http://www.uonbi.ac.ke/staff/vmadadi
12/13/2011 mov 1
Introduction
• Kinetics is the study of rates of chemical reactions and the mechanisms by which they occur. • The reaction rate is the increase in concentration of a product per unit time or decrease in concentration of a reactant per unit time. • A reaction mechanism is the series of molecular steps by which a reaction occurs.
12/13/2011
mov
2
1
13/12/2011
Reaction rate
2 NO2(g) → 2 NO(g) + O2(g)
12/13/2011
mov
3
Thermodynamic vs kinetics of reaction
• Thermodynamics determines if a reaction can occur. Kinetics determines how quickly a reaction occurs • Some reactions that are thermodynamically feasible are kinetically so slow as to be imperceptible • The Rate of a Reaction Cdiamond + O2(g)→ CO2(g) ΔG°= -396kJ Very Slow H+(aq) + OH-(aq) → H2O(l) ΔG°= -79kJ 12/13/2011 Very Fastmov
4
2
13/12/2011
Rate of chemical reaction
• 2 N2O5 → 4 NO2 + O2 • 2 moles of N2O5 disappear for every 4 moles of NO2 and 1 mole of O2 formed. • Reaction rates are the rates at which reactants disappear or products appear.
12/13/2011
mov
5
Reaction rate
• Reaction rate is the change of concentration of a reactant or product per unit time aA + bB → cC + Dd Reaction rate = ΔConcentration Δtime
• Rate is expressed either as rate of appearance of product or rate of disappearance of reactant • E.g. aA + bB → cC + dD
12/13/2011 mov 6
3
13/12/2011
Reaction rate
• Mathematically, the rate of a reaction can be written as:
•
Square brackets [ ] are often used to express molarity (i.e.[HCl] means Molarity of HCl) The relative rates of consumption of