Unit 2.5 Flashcards Preview

Chemistry 12 > Unit 2.5 > Flashcards

Flashcards in Unit 2.5 Deck (62)
Loading flashcards...
1

reaction rate

change in concentration of a reactant or product per unit time

2

rate as time goes on

should decrease and be as close to 0 as possible (reaction is "finished")

3

instantaneous rate vs. average rate

average rate: just the slope of the change in reactant over time

instantaneous rate: shows rate at a certain point in time

4

rate law

shows how the rate depends on the concentrations of reactants

5

why don't products appear in the rate law?

the concentrations of the products do not appear in the rate law because the reaction rate is being studied under conditions where the reverse reaction does not contribute to the overall rate

6

integrated rate law

shows how concentration depend on time

7

how to measure the rate of reaction of a gas

- water displacement measures the volume of H2/ the rate that the volume changes is equal to the rate that the moles change which can give you the concentration/time
- with concentration measuring probes
- can measure the rate that the mass of a solution goes down by a scale

8

how to measure rate of reaction when solid is the limiting reagent

measures the mass/time which can be moles/ time

9

how to measure rate of reaction when acid/base

measure pH to translate to concentration of H+. as the concentration of H+ shows how much more acidic/basic a solution is getting

10

how to measure rate of reaction when coloured compound

measure the rate that the colour disappears/appears (qualitative) or measure using a colorimeter

11

how to measure rate of reaction when opaque

this is also relative using the disappearing cross experiment

12

rate of appearance/disappearance

when calculating the rate of change of the reactants disappearing, a negative sign is added to make the rate positive

13

how does rate of reaction make sense

10 mol/s means 10 moles of reactions occur each second, not that 10 moles of chemical actually react. 6.02 x 10^23 times molecules number of reactions

14

k

contains al the factors such as temperature, steric factor, reactivity etc. and the units can vary

15

order

shows how much of an effect changing the concentration of one variable has on the rate

ex. order 2 is doubled
= quadrupled reaction

16

overall order

sum of the exponents. a higher total order means more dependent/sensitive reaction to concentration

17

when given the concentration of a reactant and the eqn

don't multiply the concentration by the coefficient!

18

initial rate

the initial rate at which the reactants combine
experimentally: measure the instantaneous rate at t=0

19

nuclear decay

first order reaction

20

collision theory

molecules must collide to react however majority of collisions do not lead to a reaction

21

collision theory concentration

rate increases as the concentration of reactants increase

22

transition state/activated complex

bonds go through a transition state. the species at the transition state is called the activated complex. this is very unstable

23

activation energy

reactants must collide with enough energy to form the activated complex

24

temperature

at high temperature means that the molecules have a greater average kinetic energy which means the collision will have more energy to overcome the activation energy

25

steric factor

A, a number that represents the likelihood that a collision occurs with the right geometry.

decreasing the size, increases the rate of reaction
increases the surface area available for collisions to take place

26

reaction mechanism

the process by which a reaction occurs

27

each collision in a mechanism is called

elementary step

28

elementary steps

- can be uni or bimolecular (1 or 2 molecules reacting)

29

rate determining step

the slowest elementary step determines the rate of the overall reaction
- the order is the coefficient since each reactant is the coefficient

30

a valid mechanism

1. sum of elementary steps must give the overall reaction
2. the rate law based on the RDS must be consistent with the experimental rate law
3. no elementary step includes more than 2 reactants