1. Chapter 6.1 Reaction Rates

2. Key Terms
Chemical kinetics is the area of chemistry that deals with rates of reactions
Reaction rate is the change in concentration of a reactant or product of a chemical reaction per unit time.

3. Measuring Reaction Rate
Formation of a gas (collect it)
Colour change (spectrophotometer)
Mass
pH (pH meter, pH paper, or a pH indicator)
Electrical conductivity (caused by formation of ions)
** Read pages !

4. Average Reaction Rate We can rewrite the equation as:
Where Δ indicates the change in quantity
chemical symbols in square brackets, [ ], indicate the entity’s concentration, in mol/L.

5. Calculate Average Rates of Appearance
Using values from table 1 calculate the average rate of appearance of nitric oxide gas over the first 50 s of the chemical reaction.

6. Calculate Average Rate of Disappearance
Using values from table 1, calculate the average rate of disappearance of nitrogen dioxide gas over the first 100 s of the reaction.

7. Math Review!
Secant is a straight line that intersects two points on a curve
Tangent is a straight line that touches a curve at a single point and does not cross through the curve.

8. Average Rate of Reaction
Slope is a measure of the steepness of a line relative to the horizontal axis
On a concentration vs. time graph, the average rate of reaction is equal to the slope of the secant line.

9. Determine the Average Rate Using a Graph
Use the graph to determine the average reaction rate for the production of oxygen gas between 180 s and 320 s.

10. Instantaneous Rate of Reaction
We can use concentration vs. time graphs to determine the rate of reaction at any single instant by finding the slope of the tangent to the curve at that instant.

11. Determine Instantaneous Rate of Appearance
Using the graph, calculate the instantaneous rate of appearance of oxygen gas at 250 s.

12. Recall…

13. So if we were to calculate the rate of reaction from our previous examples…

14. Stoichiometric Rate Relationship
Ex. 1: Write the stoichiometric rate relationship between products and reactants for the decomposition of dinitrogen pentoxide. 2 N2O5(g)  4 NO2(g) + O2(g)

15. Stoichiometric Rate Relationship
Ex. 2: If the rate of disappearance of N2O5 is 5.6x10 -2 mol/L at 60s, determine the rate of appearance of oxygen at the same time. 2 N2O5(g)  4 NO2(g) + O2(g)

16. Stoichiometric Rate Relationship
Ex3. Calculate the rate of appearance of NO2 at 90s if the rate of appearance of oxygen gas at this time is 2.0x10-2 mol/Ls. 2 N2O5(g)  4 NO2(g) + O2(g)

17. HOMEWORK
P.350 #1
P. 360 #1 – 3
P. 361 #1 – 3