Journal Entry1. What is rate?2. Do all reactions occur at the same rate?3. Give examples of reactions that have

different rates?4. Give examples of reactions that occur at

different rates under different conditions5. Give examples of processes that cannot be

controlled6. Give examples of processes that can be

controlled

Practice Redox Problems

• Ag(s) + HNO3(aq) AgNO3(aq) + NO(g) + H2O(l)

• C3H8O(aq) + CrO3(g) +H2SO4(aq) Cr2(SO4)3(aq) + C3H6O(aq) + H2O(l)

• I-(aq) + HSO4

-(aq) I2(s) + SO2(g) (acidic)

• CrO42-

(aq) + S2-(aq) S(s) + CrO2-

(g)

• Sb(s) + HNO3(aq) Sb2O5(s) + NO(g) + H2O(l)

• KOH(aq) + Cl2(g) KCl(aq) + KClO(aq) + H2O(l)

• Zn(s) + NO3-(aq) Zn2+

(aq) + NO(g) (acidic)

• MnO4-(aq) + SO3

2-(aq) MnO2(s) + SO4

2-(aq) (basic)

Unit 3: Kinetics

Lesson1: Reaction Rate

Different kinds of rates

• Rate of reaction• Rate of reading• Rate of population growth

Chemical Kinetics• The study of whether or not a reaction will

occur• How fast a reactant disappears or how fast a

product appears• Fireworks vs. Digestion

Average reaction rate =

-∆Reactant= ∆ProductTime Time

the symbol ∆ means ``the change in``Therefore,= [Reactant]final - [Reactant]initial

Timefinal-Timeinitial

= [Product]final- [product]initial

Timefinal-Timeinitial

2NH3(g) 3H2(g) + N2(g)

• Hydrogen is formed 3 times faster than nitrogen

∆[H2] = 3 x ∆[N2] OR 1 x ∆[H2] = ∆[N2]

∆t ∆t 3 ∆t ∆t

• One mole of nitrogen forms, two moles of ammonia decompose

-∆[NH3] = 2 x ∆[N2]OR -1 x ∆[NH3] = ∆[N2]

∆t ∆t 2 ∆t ∆t

2NH3(g) 3H2(g) + N2(g)

Overall reaction rate relationship:-1 x ∆[NH3] = ∆[N2] = 1 x ∆[H2]

2 ∆t ∆t 3 ∆t

rate[H2] = 6.0 x 10-2 mol/L s∙Rate [N2] = 2.0 x 10-2 mol/L s∙

Rate[NH3] = -4.0 x 10-2 mol/L s = 4.0 x 10∙ -2 mol/L s ∙

2NH3(g) 3H2(g) + N2(g)

Average rate of any reaction

aA + bB cC + dD

Can be determined by using the inverse of each coefficient in the chemical equation

1 x ∆[C] = 1 x ∆[D] = -1 x ∆[A] = -1 x ∆[B]c ∆t d ∆t a ∆t b ∆t

[C4H9Cl] (M) vs Time (sec)

0 100 200 300 400 500 600 700 800 9000

0.02

0.04

0.06

0.08

0.1

0.12

Y-Values

Time (sec)

[C4H

9Cl]

(M)

Instantaneous Rate• Find the slope of the line.

Inst. Rate = ∆[C4H9Cl] = 0.025mol/L – 0.065 mol/L

∆t 600s – 200s

= 1 x 10-4 mol/L

***BEDMAS***

Determining Reaction Rate

• monitoring of mass, pH, and conductivityMg(s) + 2HCl(aq) MgCl2(aq) + H2(g)

- Mass will decrease (H2 escaping)- pH will increase (getting more basic as HCl is used

up)- Use change in conductivity to determine reaction

rate of reactant ions forming product ions

Determining Reaction Rate

• Monitoring of pressure– When reactions involve gases, the pressure of the

system changes

2N2O5 4NO2 + O2

-pressure increases as two moles of N2O5 decompose into 5 moles of gaseous products

• Monitoring colour and volume– Absorption of light is directly proportional to

concentration (mol/L)– In gases, they can be collected in an inverted tube

& measured by displacement

Determining Reaction Rate

• Monitoring of temperature– Using a temperature probe– Increase for exothermic (heat given off or exiting!)– Decrease for endothermic (heat absorbed)

Determining Reaction Rate

Why reaction rates?

• Ex. Knowing reaction rate can help doctors control insulin production in the body

• Ex. Industrial chemists might want to speed up ammonia production for fertilizers

Reaction Rate Reaction TimeDescribes the change over time that a reaction proceeds at.

Merely the amount of time that a reaction takes to occur.

Example: @ 508°C 2HI(g) H2(g) + I2(g)

Time (s) [HI] (mol/L0 0.100050 0.0716100 0.0558150 0.0457200 0.0387250 0.0336300 0.0296350 0.0265

GRAPH [HI] VS. TIME

0 50 100 150 200 250 300 350 4000

0.02

0.04

0.06

0.08

0.1

0.12

[HI] vs. Time

Time(s)

[HI]

(mol

/L)

• Calculate the average rate from 0-350 secondsAvg rate = Cf – Ci

Tf-Ti

• Calculate the instantaneous rate at 0 seconds• (draw a tangent line)Inst. rate = Cf – Ci

Tf-Ti

• Calculate the instantaneous rate at 100 seconds

• (draw a tangent line)Inst. rate = Cf – Ci

Tf-Ti