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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.
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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 + Potential Energy Kinetic Energy Kinetic Energy Kinetic Energy Kinetic Energy
Effect of Particle Size (surface area) Rate of reaction increases with increased surface area(crushing, grinding) . Moreparticlesinvolved, morefrequentcollisions, higherchancesof successful collisions.
Effect of Concentration Rate of reaction increases with increased concentration (mol/L) of particles. Moreparticlesinvolved, morefrequentcollisions, higherchancesof successful collisions.
Effect of Pressure Only affects reaction rates of gaseous reactions. Rate of reaction increases with decreased volume of the container - mimics higher [ ]. Closerparticles, morefrequent collisions, higherchancesof successful collisions.
Effects of a Temperature Change Rate of reaction increases with increased temperature. Morekinetic energy, moreparticles with EA, higherchancesof successful collisions.
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)
2. Comparing reactions with similar bond numbers Covalent takes longer to break than aqueous ionic (aq):already separated into ions, so instantaneous reaction. H2(g) + I2(g) → 2 HI(g) KNO3(aq) + NaI(aq) → KI(aq) + 2 NaNO3(aq)
Ionic compounds in solution separateinto ions – no “bonds” to break. KNO3(aq) + NaI(aq)→ KI(aq) + NaNO3(aq) Na+ K+ I- NO3-
3. Comparing similar compounds and similar bond numbers (g) faster> (l) > (s) • Less Intermolecular forces to overcome • More KE per particle • More surface area • More COLLISIONS
Effect of Catalysts • A catalyst speeds up areactionby lowering EA • Does not alter products or ΔH. • Appears unchanged. • Often not shown in the overall chemical reaction Enzymes are known as biological catalysts. An inhibitor is the opposite of a catalyst.
Catalyst: Lower EA Activation Energy
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