# Lecture 26: Addition Reactions and Chemical Kinetics

### Addition Reaction

- Takes place on a double bond
- Electrophile to C$=$C

#### Halogens

### Chemical Kinetics

**Reaction Rates** - Measure how quickly they proceed in a given time. The speed of a chemical reaction is usually reported as its change in concentration (molarity) over time, molarity per second (M/s)

Average rate of appearance of $B = \frac{change \ in \ [B] }{change \ in \ time} = \frac{\Delta [B]}{\Delta t}$

Average Rate of Disappearance of $A = \frac{change \ in \ [B]}{change \ in \ time} = - \frac{\Delta[A]}{\Delta t}$

- Decreases and converts to $B$

**Relative Reaction Rate Equations -** $\frac {\Delta B}{\Delta t}, \ \frac {\Delta [A]}{\Delta t}$

$*$Rate of reaction decreases as the reaction proceeds because as the reaction proceeds, the amount of reactants decreases.

**Overall Equation** - For reaction: $2HI_{(g)} \rightarrow H_{2(g)} + I _ {2(g)}$

$- \frac{1}{2} \frac{\Delta [HI]}{\Delta t} = \frac {\Delta [H_2]}{\Delta t }= \frac {\Delta [I_2]}{\Delta t}$

$aA + bB \rightarrow cC + dD$

$- \frac{1}{a} \frac{\Delta [A]}{\Delta t} = - \frac{1}{b} \frac {\Delta [B]} {\Delta t}$$= \frac{1}{c} \frac{\Delta [C]}{\Delta t} = \frac{1}{d} \frac {\Delta [D]} {\Delta t}$

Relationship between the rate and specific concentration is presented by the reaction order of a particular substance.

If doubling the concentration of one reactant $\Rightarrow$ Rate doubles

$=$ First order Reaction

If doubling the concentration and the rate quadruples

$=$ Reaction is Second Order

If it doesn't effect the rate, it is $=$ zero order

The overall Reaction order is the sum of the orders from the individual reactants $=$ if a reaction is first order with respect to each reaction it is overall second order

#### Rate Law

$aA + bB + cC \rightarrow dD + eE$

rate $= K[A]^m [B]^n [C]^p$

$m=$ order with respect to $A$ $( m \neq a)$

Not the coefficient from the equation. $m$ is expressed

#### Experimentally,

**Initial Rates Data** - Experimental technique to find $m/n/p$ by changing the initial concentrations of one reactant at a time then we can see the effect of one reactants concentration on the rate.

$K =$ rate $\cdot$ constant (units)

**First Order -** $1/s$

**Second Order - **$1/(s \cdot m)$

**ZERO Order -** $m/s$

#### Integrated Rate Laws

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