PSU Chem 112 first exam questions and answers 100% correct answers

formula for rate - correct answers ∆concentration/∆time effect of concentration on rate of reaction - correct answers increased concentration means an increase in the probability of having more collisions, increasing the rate of reaction effect of temperature on rate of reaction - correct answers molecules must collide with enough kinetic energy to react, increasing the temperature increases the kinetic energy which makes collision more likely and increases the chance that a collision will cause a reaction | increasing the temperature will increase the rate of reaction rate of an a-b reaction - correct answers -∆[A]/∆t = ∆[B]/∆t | reactants are positive slope of a rate graph - correct answers ∆[A]/∆t rate of aA-bB - correct answers (-1/a)(∆[A]/∆t) = (1/b)(∆[B]/∆t) ratio of stoichiometric coefficient rate law - correct answers expresses the rate as a function of change in concentration over change of time rate law for aA+bB-cC+dD - correct answers rate=k[A]^m * [B]^n reaction order - correct answers show how the rate is affected by the reactant concentration three reaction orders - correct answers 0= change concentration and it doesn't affect rate 1= double concentration double rate 2= double concentration quadruple rate overall order - correct answers orders all summed up units of k for zero first second and third order - correct answers zero= ms⁻¹ first=s⁻¹ second=m⁻¹s⁻¹ third=m⁻²s⁻¹ find order in respect to a reactant equation - correct answers (rate x / rate y)= ([ ]x / [ ]y)^m find order of reactant - correct answers find two experiments where only concentration is changing is the one youre looking for then use the comparison equation find the rate constant k - correct answers find both orders of both reactants then pick an experiment plug in all the values and solve for k integrated rate laws - correct answers used to find the time it takes to use up a specific amount of a reactant and the amount of reactant used up in a specific time interval first order integrated rate law - correct answers ln[A]=ln[A]₀ -kt second order integrated rate law - correct answers 1/[A]t = 1/[A]₀ +kt graph of what vs time is a first order - correct answers ln[A] graph of what vs time is a second order - correct answers 1/[A] positive vs negative slope first and second order - correct answers negative slope= first order positive slope=second order y intercept of first and second order graphs - correct answers first= ln[A₀] second= 1/[A₀] how to determine the concentration of a reactant at a certain time after the initial using a graph - correct answers 1. determine if its first or second order based on which graph is best fit 2. use the integrated rate law for that order 3. get k from the slope, and initial concentration from the y intercept 4. solve out for final concentration formula to relate half life to rate constant - correct answers half life = .693 / k increase of temperature does what to activation energy - correct answers increases fraction of collisions that have enough energy to exceed it endothermic vs exothermic graphs, products higher or lower - correct answers exothermic=reactants higher than products endothermic= reactants lower than products the activation energy is which part of the graph - correct answers the height from the reactants to the highest point the higher the activation energy the ___ the reaction - correct answers slower catalysits only affect __ not ___ (Ea or ∆H) - correct answers dont affect ∆H only Ea arrhenius equation when theres a change in temperature - correct answers ln(k1/k2) = Ea / 8.314 (1/T2 - 1/T1) formula for an arrhenius plot - correct answers ln(k) = -Ea /RT + Ln(A) mechanisms - correct answers the sequence of molecular collisions needed to go from reactant to product |||| series of elementary steps rate determining step - correct answers one that takes the longest rate law of unimolecular elementary step (a- B+C) - correct answers r=k[A] rate law of bimolecular elementary step of (A+B-C+D) - correct answers r=k[A][B] rate law of bimolecular elementary step of (2A-C+D) - correct answers r=k[A]² rate law of termolecular elementary step (A+B+C-D+E) - correct answers r=k[A][B][C] intermediates - correct answers species in reactions that are formed during an intermediate step but dont exist in produts intermediates (never/always) appear in rate law - correct answers never in a multi step reaction, intermediates will first appear as __ then later as ___ - correct answers products, reactants catalyist - correct answers substance that increases the rate of reaction without being consumed in the reaction how does a catalyst work - correct answers lowers the activation energy and therefore increases overall rate ||| provides a different mechanism for the reaction of lower energy does a catalyst increase yield - correct answers no just speeds up does a catalyst increase the heat of the reaction - correct answers no catalysts (always/never) appear in rate law - correct answers never in a multi step reaction, catalysts will first appear as ___ and later as ___ - correct answers reactants, prodcuts how to tell what is a catalyst and what is an intermediate - correct answers write out entire reaction, cross out what appears on both sides, determine among those elements which one is catalyst or intermediate by seeing if it goes from product to reactant etc transition state - correct answers top of the hill when activation energy is reached find activation energy formula - correct answers k=Ae ^(-Ea/RT) half life of second order - correct answers t1/2= 1/k[A]₀ when slow step comes first - correct answers rate law is the products