IMG_0824.HEIC

# Chemistry 102 ## Chapter 14: Chemical Kinetics ### Chemical Kinetics \- studies the speed or rate of reactions ### Reaction Rate rate = $\frac{\Delta [A]}{\Delta t}$ \- change in concentration of A over a period of time \- can be expressed as: * the rate of disappearance of reactant *...

# Chemistry 102 ## Chapter 14: Chemical Kinetics ### Chemical Kinetics \- studies the speed or rate of reactions ### Reaction Rate rate = $\frac{\Delta [A]}{\Delta t}$ \- change in concentration of A over a period of time \- can be expressed as: * the rate of disappearance of reactant * the rate of appearance of product **Example:** $H_2(g) + I_2(g) \rightarrow 2HI(g)$ rate = $-\frac{\Delta [H_2]}{\Delta t}$ = $-\frac{\Delta [I_2]}{\Delta t}$ = $\frac{1}{2}\frac{\Delta [HI]}{\Delta t}$ ### General Rate Expression $aA + bB \rightarrow cC + dD$ rate = $-\frac{1}{a}\frac{\Delta [A]}{\Delta t}$ = $-\frac{1}{b}\frac{\Delta [B]}{\Delta t}$ = $\frac{1}{c}\frac{\Delta [C]}{\Delta t}$ = $\frac{1}{d}\frac{\Delta [D]}{\Delta t}$ ### Factors Affecting Reaction Rate 1. Reactant Concentration \- higher concentration, higher rate 2. Temperature \- higher temperature, higher rate 3. Catalysts \- affect rate without being in overall balanced equation 4. Surface Area \- increased surface area, increased rate ### Rate Laws \- expresses rate as a function of concentration and rate constant $aA + bB \rightarrow cC + dD$ rate = $k[A]^x[B]^y$ * k = rate constant * x = order of reaction with respect to A * y = order of reaction with respect to B * x + y = overall order of reaction **Note:** Orders must be determined experimentally, they are not derived from stoichiometry