Rate Equation

Question 1

What is the rate of a chemical reaction related to

Answer 1

The concentration of the reactants by a rate euqation

Question 2

What is an example rate equation

Answer 2

Rate = K[A]^n [B]^n
m and n are the orders of reaction
A and B are reactant
K is rate constant

Question 3

What effects the rate equation constant ( what formula supports this)

Answer 3

Temperature
The Arrhenius equation
K = Ae^-Ea/RT

Question 4

What is the Arrhenius equation

Answer 4

K = Ae^-Ea/RT
A is a constant (same units as the rate constant)
Ea = activation energy
T = temp in kelvin

Question 5

What is the rearranged version of the Arrhenius equation

Answer 5

Ln K = (-Ea / RT) + Ln A

Question 6

What is the rearranged version of the Arrhenius equation used for

Answer 6

Plotting a straight line graph of rate of reaction

Question 7

How can you plot a graph using the rearranged version of the rate equation

Answer 7

Plot Ln K on the Y axis
Plot 1/T on the x axis
Ln A will be the Y intercept
Grad = -Ea/R

Y = m x + C
Ln k =(-ea/R) (1/t) + LnA

Question 8

How many degrees does it take to double rate of reaction

Answer 8

10

Question 9

How is the rate equation determined

Answer 9

Experimentally

Question 10

What is the rate determining step

Answer 10

The slowest stage of a chemical reaction

Question 11

What is the order of reaction

Answer 11

The power to which the concentration of that reactant is raised in the rate equation

Question 12

rate = k[E]
Explain qualitatively why doubling the temperature has a much greater effect on the rate of the reaction than doubling the concentration of E.

Answer 12

1. Reaction occurs when molecules have E>Ea
2. Doubling T by 10 °C causes many more molecules to have this E
3. Whereas doubling [E] only doubles the number with this E

Question 13

What are orders of reactions restricted to

Rate equations

Answer 13

0,1,2

Question 14

Why can the order of a reaction with respect to a very concentrated chemical be ignored in this experiment.

Answer 14

The concentration/amount of the chemical is much larger than the concentration/amount of the other reactant

Concentration of highly concentrated reaction is (almost) constant

Question 15

Why may a graph of reactant volume against time is 0 order

Answer 15

The graph is a straight line / has a constant gradient

So the rate of reaction does not change as the concentration (of iodine) changes / the iodine is being used up at a constant rate.

(If Iodine was first order, the graph would slow down)

Question 16

What is the overall order of a reaction

Answer 16

The sum of powers (to which the concentrations are raised in the rate equation)