Rate of reactions, exo. & endo.

Question 1

what affects rates of reactions

Answer 1

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

Question 2

define successful collision

Answer 2

-collisions with enough energy to react

Question 3

ways to measure rate of reaction

Answer 3

-loss of mass
-volume of gas produced

Question 4

things needed for a reaction

Answer 4

particles need to collide with enough energy to start a reaction

Question 5

how to write a conclusion

Answer 5

-describe results
-explain - why

Question 6

define anomaly

Answer 6

resultthat doesnt fit the pattern

Question 7

conclusion for temp.

Answer 7

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

Question 8

why does rate of reaction decrease after 50%

Answer 8

-there are less reactant particles

Question 9

formula for average rate of reaction

Answer 9

-total mass lost/ time

Question 10

how to find rate of reaction on graph

Answer 10

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

Question 11

sodium thiosulfate + hydrochloric acid ->

Answer 11

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

Question 12

does concentration affect activation energy

Answer 12

no

Question 13

how to increase concentration

Answer 13

-increase no. particles
-decrease volume

Question 14

conclusion for concentration/ pressure

Answer 14

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

Question 15

define limiting reactant

Answer 15

reactant that is used up first in a reaction

Question 16

relationship of Surface area & particle size

Answer 16

-more surface area
-smaller particle size

Question 17

conclusion of surface area

Answer 17

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

Question 18

define activation energy

Answer 18

The minimum energy colliding particles require to react

Question 19

define catalyst

Answer 19

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

Question 20

what does catalyst do to activation energy

Answer 20

-lower activation energy

Question 21

conclusion of catalysts

Answer 21

-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

Question 22

more successful collisions or more frequent collisions

Answer 22

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

Question 23

types of reaction

Answer 23

-exothermic
-endothermic

Question 24

define exothermic reaction

Answer 24

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

Question 25

define endothermic reaction

Answer 25

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

Question 26

what must you do to break and make bonds

Answer 26

-break = absorb energy
-make = release energy

Question 27

what type of reaction is neutralization reaction

Answer 27

exothermic

Question 28

what happens to system & surr. in exo.

Answer 28

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

Question 29

what happens to system & surr. in exdo.

Answer 29

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

Question 30

what do you call heat energy

Answer 30

-Enthalpy
-H

Question 31

what is ( - ) ve & ( + ) ve

Answer 31

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

Question 32

what is in the system

Answer 32

reactants & porducts

Question 33

what is system & surr. in energy

Answer 33

-system = chemical energy
-surr. = heat energy

Question 34

how do you draw a graph for exo. reaction

Answer 34

-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

Question 35

how do you draw a graph for endo. reaction

Answer 35

-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

Question 36

symbol for activation energy

Answer 36

-Ea
(a is subscript)

Question 37

define Enthalpy change

Answer 37

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

Question 38

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

Answer 38

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

Question 39

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

Answer 39

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