Presentation on theme: "Question of the Day ΔG determines whether or not a reaction will _____, but even a spontaneous reaction can be very _________. Day 2 2-27 GO SLOW."— Presentation transcript:
Question of the Day ΔG determines whether or not a reaction will _____, but even a spontaneous reaction can be very _________. Day 2 2-27 GO SLOW
Objective How fast / slow do reactions go? Day 2 2-27
Reaction Rates Intro. to Rxn Rates & Collision Theory: Rates of reaction determine how fast a reaction goes. Usually expressed as the change in amount of reactant or product per unit time (moles / unit time)
Reaction Rates Collision Theory: = atoms, ions, and molecules can react to form products, if and only if, they collide with enough kinetic energy. If they do not have enough kinetic energy to react they bounce apart unchanged.
Reaction Rates Collision Theory: The minimum energy that colliding particles must have to react is called activation energy.
Factors Affecting Rxn Rates: 1. Temperature at higher temps. particles move faster and so frequency of collisions increases along with the kinetic energy of particles… activation energy overcome easier
Reaction Rates Factors Affecting Rxn Rates: 2. Concentration increasing concentration increases frequency of collision… activation energy overcome easier
Reaction Rates Factors Affecting Rxn Rates: 3. Particle size smaller particle size = greater surface area and so more reactant available for reaction so frequency of collisions increases… activation energy overcome easier
Reaction Rates Factors Affecting Rxn Rates: 4. Catalyst catalyst = a substance that speeds up the rate of reaction without being changed itself a catalyst speeds up the reaction by helping the reactants reach their activated complex (by decreasing the needed activation energy)
Reaction Rates Factors Affecting Rxn Rates: 4. Catalyst A catalyst is not changed during reaction, therefore it is NOT written as a reactant or product, but usually over the yield arrow: 2H 2(g) + O 2(g) 2H 2 O (g) Pt