Factors Affecting Reaction Rates temperature concentration or pressure of a reactant surface area (particle size) presence/absence of a catalyst. nature of the reactants

Quantitatively identify factors that affect the rate of a chemical reaction. Include: nature of reactants, surface area, concentration, pressure, volume, temperature, and catalyst. Describe the relationship between these factors and the relative rate using the Collision Theory. Additional KEY Terms

2 H2 + O2 → 2 H2O AC EA -∆H +

More particles involved, more frequent collisions. Effect of Particle Size (surface area) Rate of reaction increases with increased surface area (crushing, grinding) . More particles involved, more frequent collisions.

Effect of Concentration Rate of reaction increases with increased concentration (mol/L) of particles. More particles with activation energy - more chances of a successful collision.

Closer particles – more chance of collisions. Effect of Pressure Only affects reaction rates of gaseous reactions. Rate of reaction increases with decreased volume of the container - mimics higher [ ]. Closer particles – more chance of collisions.

More KE per particle – more frequent collisions and more EA. Effects of a Temperature Change Rate of reaction increases with increased temperature. More KE per particle – more frequent collisions and more EA.

10°C increase in temp usually doubles reaction rate.

Less bonds to break, faster the reaction. Effect of the Nature of Reactants 1. Comparing reactions with similar compounds: Less bonds to break, faster the reaction. 2 NO(g) + O2(g) → 2 NO2(g) 2 C8H18(g) + 25 O2(g) → 16 CO2(g) + 18 H2O(g)

KNO3(aq) + NaI(aq) → KI(aq) + 2 NaNO3(aq) 2. Comparing reactions with similar bond numbers: Covalent bonds takes longer to break than aqueous. (aq) are already separated into ions, so are instantaneous. H2(g) + I2(g) → 2 HI(g) KNO3(aq) + NaI(aq) → KI(aq) + 2 NaNO3(aq)

KNO3(aq) + NaI(aq)→ KI(aq) + NaNO3(aq)

(g) faster > (l) > (s) 3. Comparing similar compounds and similar bond numbers: (g) faster > (l) > (s) Stronger IMF to overcome Less KE per particle Less collisions Less Surface area

Effect of Catalysts A catalyst speeds up or starts a reaction by lowering the activation energy. Does not alter products or ΔH. Not involved in the overall chemical reaction Appears unchanged. Enzymes are known as biological catalysts. An inhibitor is the opposite of a catalyst.

Things that increase reaction rate: increased surface area increased concentration increased pressure increased temperature fewer bonds, aqueous or gas states catalyst To decrease reaction rate - do the opposite....

CAN YOU / HAVE YOU? Quantitatively identify factors that affect the rate of a chemical reaction. Include: nature of reactants, surface area, concentration, pressure, volume, temperature, and catalyst. Describe the relationship between these factors and the relative rate using the Collision Theory. Additional KEY Terms