kinetics Flashcards

(31 cards)

1
Q

state when reactions occur?

A

when collisions take place between particles with sufficient energy to break the bonds in the correct orientation

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2
Q

what 2 factors does the rate depend on?

A

frequency of collisions and success of collisions

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3
Q

in order to increase the rate of reaction we need to increase the number of ……?

A

succesful collisions

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4
Q

what are 4 things we can add/change to influence the rate?

A

add catalyst, change temp, pressure, surface area

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5
Q

how can an increase in concentration increase pressure ?

A

more particles present in a given volume so increase in pressure

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6
Q

define activation energy

A

minimum energy needed to start a reaction

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7
Q

define rate of reaction

A

speed at which a chemical reaction takes place

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8
Q

state rate of reaction units

A

mol dm^-3 s^-1

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9
Q

state what an ineffective collision is

A

when particles collide in wrong orientation or not enough energy to bounce off each other without causing a reaction

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10
Q

state the meaning of collision frequency ?

A

number of collisions per unit time

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11
Q

why does a Maxwell boltzsman start at the origin ?

A

no particles have zero energy

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12
Q

what and where is the most probable energy on a Maxwell boltzsman and why?

A

the energy that most particles have, at the peak on the curve because that is where most particle are

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13
Q

what does the area under the curve of a Maxwell boltzsman represent ?

A

number of particles

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14
Q

label the y and x axis on a Maxwell boltzsman graph

A

y- number of particles / molecules
x- energy

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15
Q

where would the mean energy be on a Maxwell boltzsman graph ?

A

to the right of the peak because there are some particle that have higher energy that the MPE which brings the average up

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16
Q

what happens to a Maxwell boltzsman distribution when temperature is lowered ?

A

area under curve stays same
peak moves left (lower energy )
peaks gets higher and more particles having less energy

17
Q

what happens to a Maxwell boltzsman distribution when temperature is increased ?

A

peak gets higher and lower

18
Q

in an exothermic reaction do particles or reactants have higher energy?

19
Q

in an endothermic reaction do particles or reactants have higher energy?

20
Q

what does an increase In reaction rate mean for the Ea?

A

greater proportion of molecules have energy equal or higher than Ea

21
Q

how does a catalyst increase rate if reaction ?

A

provides an alternate pathway for a reaction, one which has lower Ea. it is chemically unchanged

22
Q

what effect does increasing concentration have on the rate of reaction ?

A

more particles in a given volume in the higher concentration solution therefore increasing the number of successful collisions and increasing the rate of reaction

23
Q

what effect does increasing temperature have on the rate of reaction ?

A

particles have higher kinetic energy so more frequent collisions and increases rate of reaction

24
Q

what effect does increasing pressure have on the rate of reaction ?

A

particles closer and collide more often (more frequent collisions) so a higher chance of a reaction starting

25
what is a homogenous catalyst?
catalyst in same phase as the reactants
26
what is a heterogenous catalyst ?
catalyst in different phase as the reactants
27
explain the effect that a catalyst has on a Maxwell-boltzman ?
shifts Ea to left because more particles to the right of the Ea
28
why do most reactions not take place?
don't have sufficient energy or in the wrong orientation
29
why would a small temperature increase lead to a big increase in rate?
a higher percentage of collisions will result in a reaction
30
what does an increase in temperature do to the Ea ?
more molecules will have enough energy to react (higher than Ea)
31
state the effect a catalyst has on enthalpy change
it won't effect it