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Chem > Chap 6 - Rate of reactions, exo. & endo. > Flashcards

Chap 6 - Rate of reactions, exo. & endo. Flashcards

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1
Q

what affects rates of reactions

A

-temp
-concentration
-pressure of gas
-Surface area of solids
-catalysts

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2
Q

define successful collision

A

-collisions with enough energy to react

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3
Q

ways to measure rate of reaction

A

-loss of mass
-volume of gas produced

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4
Q

things needed for a reaction

A

particles need to collide with enough energy to start a reaction

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5
Q

how to write a conclusion

A

-describe results
-explain - why

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6
Q

define anomaly

A

resultthat doesnt fit the pattern

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7
Q

conclusion for temp.

A

-more kinetic energy
-more movement
-more frequent
-more successful collision
-faster rate of reaction

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8
Q

why does rate of reaction decrease after 50%

A

-there are less reactant particles

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9
Q

formula for average rate of reaction

A

-total mass lost/ time

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10
Q

how to find rate of reaction on graph

A

-make a tangent
-draw lines extending from tangent - make a triangle
-find gradient
-ans can vary

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11
Q

sodium thiosulfate + hydrochloric acid ->

A

-sodium chloride + water + sulfur dioxide + sulfur
-sulfur is a precipitate which makes solution cloudy

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12
Q

does concentration affect activation energy

A

no

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13
Q

how to increase concentration

A

-increase no. particles
-decrease volume

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14
Q

conclusion for concentration/ pressure

A

-more concentration
-more particles per unit volume
-more frequent collisions
-increased rate of reaction
NO ENERGY CHANGE

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15
Q

define limiting reactant

A

reactant that is used up first in a reaction

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16
Q

relationship of Surface area & particle size

A

-more surface area
-smaller particle size

17
Q

conclusion of surface area

A

-smaller particle size
-more surface area exposed to react
-more frequent collisions
-increased rate of reactions
NO ENERGY CHANGE

18
Q

define activation energy

A

The minimum energy colliding particles require to react

19
Q

define catalyst

A

-substance that speeds up the rate of a reaction but is unchanged at the end of the reaction

20
Q

what does catalyst do to activation energy

A

-lower activation energy

21
Q

conclusion of catalysts

A

-increase rate of reaction
-by lowering activation energy
-by providing an alternative reaction pathway
-more successful collisions - greater proportion of particles with energy above the activation energy

22
Q

more successful collisions or more frequent collisions

A

-temp = more frequent & successful collisions
-concentration = more frequent collisions
-surface area = more frequent collisions
-catalyst = more successful collisions

23
Q

types of reaction

A

-exothermic
-endothermic

24
Q

define exothermic reaction

A

-reaction that transfers heat energy to surrounding so temp. goes up

25
Q

define endothermic reaction

A

-reaction that absorbs heat energy from the surrounding so temp. goes down

26
Q

what must you do to break and make bonds

A

-break = absorb energy
-make = release energy

27
Q

what type of reaction is neutralization reaction

A

exothermic

28
Q

what happens to system & surr. in exo.

A

-system gives heat energy to surr.
-surr. heats up

29
Q

what happens to system & surr. in exdo.

A

-surr. gives heat energy to system
-system. heats up

30
Q

what do you call heat energy

A

-Enthalpy
-H

31
Q

what is ( - ) ve & ( + ) ve

A

-( - ) ve = negative
-( + ) ve = positive

32
Q

what is in the system

A

reactants & porducts

33
Q

what is system & surr. in energy

A

-system = chemical energy
-surr. = heat energy

34
Q

how do you draw a graph for exo. reaction

A

-Enthalpy on side
-reactants is higher than products
-reactants to products line is ΔH = -ve
-activation energy curve
-Ea is at peak of activation energy line to reactants line
-left is absorb E, right is release E
-arrows must touch
-ΔH is arrow down, Ea is arrow up

35
Q

how do you draw a graph for endo. reaction

A

-Enthalpy on side
-products is higher than reactants
-reactants to products line is ΔH = +ve
-activation energy curve
-Ea is at peak of activation energy line to reactants line
-left is absorb E, right is release E
-arrows must touch
-both arrows face up

36
Q

symbol for activation energy

A

-Ea
(a is subscript)

37
Q

define Enthalpy change

A

-The difference between the energy required to break bonds and the energy released to make bonds

38
Q

Explain an exothermic reaction in terms of bond breaking and bond making

A

-Less energy is absorbed to break bonds than energy released to make bonds

39
Q

Explain an endothermic reaction in terms of bond breaking and bond making

A

-more energy is absorbed to break bonds than energy released to make bonds

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