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63 Cards in this Set
- Front
- Back
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What are the three key factors that control rate that we can control
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Concentration
Physical state and Temperature |
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Why is concentration an important factor to rate
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Because molecules must collide in order to react. So the more molecules available to collide the faster the reaction
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Why is Physical state an important factor to rate
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molecules must mix to collide
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How do you find the reaction rate or speed of a reaction
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concentration divided by change in time
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The change in concentration divided by the change in time is also known as
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the average rate
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How do you find the rate of a reaction with the reactants
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rate=- delta[A]/delta[Time]
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If we used the products to find the rate of reaction what would it be
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rate= delta[B]/delta[time]
no negative sign |
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The rate varies with time as the reaction proceeds
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true
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Does the average rate tell us that the rate is still changing or how fast something is changing at a given instant
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no
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How can we see the rate change at a given instant
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calculate the average rate for two smaller times
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How do we graph the change in rate
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concentration vs time
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On a graph of change in rate what is the difference between the curved line and the straight line
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the curved line is a rate that is changing. The slope of the straight line is the average rate
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What is the instantaneous rate
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it is a rate at a give instant during a reaction
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What value do reactants have
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negative
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When expressing the rate in terms of Reactant and Product concentrations what equasion do you use
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rate = -1/a*delta[A]/deltaT = -1/b*delta [B]/delta T = +1/c*delta[C]/ delta T= +1/d*delta[D]/delta T
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what is K
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it is the reaction constant and is specific to a given reaction at a given temperature
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Does a change in temp change the K
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yes
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Can we find the rate law rate, reaction orders and rate constant from the stoichiometry
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no they must be found from the experiment
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How do you find the initial rate
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use concentration measurements
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How do you find the reaction orders
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use initial rates from several experiments
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How do you find the rate constant
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use the values used to find the reaction orders
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What order is rate =[A]
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first
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What order is rate =[A]2
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second
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What order is rate = [A]0
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zero
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What is the overall reaction order rate =k[NO][H2]
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second
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What is the overall reaction order of rate=[NO]2[H2]
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third
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What does a negative exponent mean
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the rate decreases when the concentration of that component increases
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Do we see negative orders for rate laws with just reactants
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no they are normally found with rate laws that include products
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what order is it if the rate doubles and then if it quadroples
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second then third
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Can we use two rates from reactions at two different temps to find a k
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no because k changes with temp
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How can we find k from the rate constant
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since rate =k[A][B] then k =rate / [A][B]
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What are the units for k at zero order
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mol/L*s
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What are the units for k at first order
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1/s
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What are the units for second order
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L/mol*s
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What are the units for third order
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L2/mol2*s
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What is the difference between regular rate laws and the integrated rate laws
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the integrated rate laws factor in time
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What is the first order integrated rate law equation
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ln[A]init/[A]fin=kt
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What is the second order integrated rate law equation
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1/[A]init-1/[A]fin=kt
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What is the zero order integrated rate law equation
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[A]fin-[A]init=-kt
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In the integrated rate law what is time measured in
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seconds
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How do you plot first order on a graph
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ln[reactant] vs time
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How do you plot second order on a graph
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1/[reactant] vs time
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How do yo plot zero order on a graph
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[reactant]vs time
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What is half life
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the time required for the reactant concentration to reach half its initial value
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How do you write the half life equation for a first order reaction
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t(1/2)=.693/k
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What is the equation for a second order reaction
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t(1/2)=1/k[A]0
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How are the second order and zero order half lives different
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the second order half life is inversely proportional to the initial reactant concentration so as the reaction proceeds the half life gets bigger the zero order half life is directly proportional to the concentration
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For many reactions around room temp what does an increase in 10 C do
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doubles or triples the rate
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What is the Arrhenius equation
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k= Ae to the -Ea/RT power
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As T increases K increases
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true
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How can the Arrhenius equation be turned into y=mx+b
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ln(k)= y
ln(A)= b -Ea/R= m 1/T= x |
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What equation do we use to solve for Ea
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ln(k2/k1)= -Ea/R(1/T2-1/T1)
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What is the value for R
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8.314
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What does temp rise do in relation to collisions
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raises the fraction of collisions with enough energy to exceed the activation energy
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When searching for the fraction of molecular collisions what equation do you use
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F= e to the -Ea/RT power
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What is a reaction energy diagram
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shows the potential energy for a reaction
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in a reaction diagram how does and endothermic reaction work
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reactants are lower than the products
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what does the delta h of the reaction equal
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the activation energy of the reaction forward- minus the activation energy of the reaction backward
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Where does the Delta h of reaction go on the diagram
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Under the reactants
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In a elementry step do we use the reaction coefficents for the rate law
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yes
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What is a catylist
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speeds up the reaction not used up and consumed in the beginning and reformed lowers activation makes same amount of product
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What is a homogenous catalyst
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exists in solution with the reaction mixture they are gasses liquids and solids
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What is a heterogenuis catalyst
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it speeds up a reaction that occurs in a separate phase the catalyst is most often solid the reaction normally occurs on the solids surface and it has a large surface area
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