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Chem 178 Chaper 14
Chemical Kinetics Review
Question | Answer |
---|---|
14.1) The study of how fast chemical reactions occur is called what? | Chemical Kinetics |
14.1) What are the four important factors that affect rates of reactions? | Physical state of the reactants, concentration of the reactants, temperature of the reaction, presence of absence of a catalyst |
14.2) How is the speed of a reaction measured? | The change that occurs per unit time |
14.2) The speed of a chemical reaction is called what? | Reaction rate |
14.2) What are the units for average rate? | M/s |
14.2) The rate at any instant in time is called what? | Instantaneous rate |
14.2) How do you measure instantaneous rate? | Find the slope of the straight line tangent to the curve at that instant |
14.2) Is there a difference between instantaneous rate and average rate? | Yes |
14.3) An instantaneous rate taken at time 0 can be called what? | Initial rate |
14.3) In general, do reaction rates increase or decrease when the concentration of reactants in increased? | Increase |
14.3) The proportionality constant, k, is called what? | Rate constant |
14.3) An equation that relates the reaction rate to the concentrations of reactants is called what? | Rate law |
14.3) The power to which the concentration of a reactant is raised in a rate law is called what? | Reaction order |
14.3) How do you find the overall reaction order? | Take the sum of the reaction orders in the rate law |
14.3) True or False, stoichiometric coefficients in the balanced chemical equation always correspond to the reaction orders. | False |
14.3) What are the three most common values for reaction orders? | 0,1, and 2 |
14.3) True or False, fractional and negative reaction orders are possible. | True |
14.3) If a reaction is zero order in a reactant, what effect will doubling the initial concentration of that reactant have on the rate? | No effect |
14.3) If a reaction is first order in a reactant, what effect will doubling the initial concentration of that reactant have on the rate? | The rate increases by a factor of two |
14.3) If a reaction is second order in a reactant, what effect will doubling the initial concentration of that reactant have on the rate? | The rate increases by a factor of four |
14.3) If a reaction is nth order in a reactant, what effect will doubling the initial concentration of that reactant have on the rate? | The rate increases by a factor of 2^n |
14.3) True or False, the rate constant depends on concentration. | False |
14.3) True or False, the rate of reaction depends on concentration. | True |
14.3) True or False, the rate constant is affected by temperature. | True |
14.3) True or False, the rate constant is affected by presence of a catalyst. | True |
14.4) A plot of the natural log of the concentration of A sub t, versus t, is a straight line with slope -k and intercept natural log of the concentration of A sub 0 in which overall order of reaction? | First |
14.4) A plot of 1 over the concentration of A sub t, versus t, is a straight line with slope k and intercept 1 over the concentration of A sub 0 in which overall order of reaction? | Second |
14.4) The time required for the concentration of a reactant to decrease to half of its original value is called what? | Half-life |
14.4) The equation half life = 0.693/k is the half life equation for which overall order of reaction? | First |
14.4) The equation half life = 1/(k times the concentration of A sub 0) is the half life equation for which overall order of reaction? | Second |
14.5) Do most reaction rates increase or decrease as temperature increases? | Increase |
14.5) True or False, for molecules to react they must collide. | True |
14.5) Is the reaction rate faster or slower with a greater number of collisions? | Faster |
14.5) Do reaction rates generally increase or decrease with an increase in the concentration of reactants? | Increase |
14.5) Should reaction rates increase or decrease with increasing temperature? | Increase |
14.5) When reactant molecules collide, what two things must occur to form products? | The molecules must collide with proper orientation and enough energy. |
14.5) The minimum energy required to initiate a chemical reaction is called what? | Activation energy |
14.5) The energy barrier between the starting molecule and the highest energy state found along the reaction pathway is called what? | Activation energy |
14.5) The species at the top of the energy barrier in a reaction pathway is called what? | Transition state or activated complex |
14.5) Is the reaction rate faster or slower with a lower activation energy? | Faster |
14.5) If a forward reaction is exothermic, is its reverse reaction exothermic or endothermic? | Exothermic |
14.5) How much energy do molecules need in proportion to the activation energy in order to have sufficient energy to react? | Equal to or greater than |
14.6) What is a reaction mechanism? | The process by which a reaction occurs |
14.6) Processes that occur in a single step are what kind of reactions? | Elementary |
14.6) What is the term for a reaction that involves just one reactant molecule? | Unimolecular |
14.6) Reactions that involve the collision of two molecules are what type of reactions? | Bimolecular |
14.6) Elementary reactions that involve the simultaneous collision of three molecules (statistically improbable) is what type of reaction? | Termolecular |
14.6) Which species appears in an elementary step but are not a reactant or product in the final balanced chemical equation? | Intermediate |
14.6) Are bimolecular processes first order, second order, or third order? | Second |
14.6) Is the rate-determining step in a multistep reaction the slowest step or the fastest step? | Slowest step |
14.6) Which step in a multistep reaction governs the overall rate law for the overall reaction? | Rate-determining step |
14.6) Can intermediates found in a multistep mechanism be used in the overall rate law? | No |
14.7) What is the name of the substance that changes the rate of a chemical reaction without itself undergoing a permanent chemical change? | Catalyst |
14.7) Does a homogeneous or a heterogeneous catalyst exist in the same phase as the reacting molecules? | Homogeneous |
14.7) How do catalysts increase reaction rates? | Lowering the overall activation energy |
14.7) Is the process of binding reactant molecules a surface called absorption or adsorption? | Adsorption |
14.7) Is the uptake of molecules into the interior of another substance called absorption or adsorption? | Absorption |
14.7) What is the term for a biological catalyst? | Enzyme |