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the rate and extent of chemical change Flashcards

1
Q

Iron can react with oxygen to form iron oxide. This is also known as rusting.
Is this a fast or slow chemical reaction?

A

slow

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2
Q

When you strike a match it causes a tiny amount of red phosphorus to be converted to white phosphorus, which then ignites spontaneously in air.

Is this a fast or slow chemical reaction?

A

fast

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3
Q

what is an example of an extremely fast reaction

A

explosions like fireworks

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4
Q

how can you measure the rate of reaction

A

you can measure how fast the products are being rpoduced
or
you can measure how fast the reactants are being used

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5
Q

what is the rate of a chemical reaction

A

how fast the reactants are changed into products

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6
Q

what does a steeper line on a rate of reaction graph mean

A

that the rate of reaction is faster

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7
Q

what does a less steep line on a rate of reaction graph mean

A

the rate of reaction is slower as the reactants are used up

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8
Q

particles must collide with enough _______ in order to _______

A

energy
react

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9
Q

what is collision frequency

A

how often the particles collide.
the more collisions there are the faster the reaction is

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10
Q

what is the minimum amount of energy that particles need to react called

A

activation energy

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11
Q

why do particles need to meet their activation energy in reactions

A

activation energy is the minimum amount of energy that particles need to break the bonds in the reactants and start the reaction

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12
Q

what happens when there are more particle collisions

A

the rate of reaction will increase

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13
Q

what is the formula for the rate of reaction

A

rate of reaction = the amount of reactant used or the amount of product formed/ time (s)

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14
Q

what are different factors that affect the rate of reaction

A
  • temperature
  • surface area
  • concentration of a solution or the pressure of gas
  • the presence of a catalyst
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15
Q

how can we increase the rate of reaction

A

by increasing the number of successful collisions between the reacting particles

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16
Q

how does increasing the temperature increase the rate of reaction

A
  • the temperature is increased making the particles move faster
  • as they move faster they are going to collide with each other more frequently
  • the faster they move the more energy they will have so more of the collisions with have the energy to make the reaction happen
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17
Q

how does increasing the concentration or pressure increase the rate of reaction

A
  • if the concentration or pressure is increased it means there will be more particles per unit of volume
  • if there are more particles it means there will be more collisions which increases the rate of reaction
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18
Q

how does increasing the surface area increases the rate of reaction

A

by increasing the surface area it increases its surface to volume ratio.

which means that for the same volume for solid the particles around it will have more area to work on so the collisions will be more frequent

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19
Q

what is a catalyst

A

a substance that speeds up a reaction without being chemically changed or used up in the process

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20
Q

how do catalysts increase the rate of reaction

A

they decrease the activation energy by providing an alternative reaction pathway with a lower activation energy

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21
Q

why type of catalyst are enzymes

A

biological catalysts meaning they catalyse in living things

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22
Q

When considering how a condition will affect the rate of reaction, you have to consider how it will affect the………

A

frequency of collisions
and the energy of the particles

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23
Q

Explain how the rate of reaction changes with increasing temperature.

A

Particles will have more energy

Particles will collide more frequently

More successful collisions

Higher rate of reaction

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24
Q

Which form of magnesium would give the highest rate of reaction?

A

powder form as there is a high surface area so it will react more quickly

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25
what are some examples of catalysts
- cobalt - enzymes - nickel
26
Should you include the catalyst in the chemical reaction as one of the reactants?
no
27
why isnt a catalyst included in a chemical reaction as one of the reactants?
because it is not chemically changed or used up in the reaction so its being used up in the reaction itself so its not included
28
Do transition metals make good catalysts?
yes
29
what does this sign mean in terms of a reaction ➔
that it is a one way reaction
30
what does this sign mean in terms of a reaction ⇌
that the reaction is reversible
31
what happens in reversible reactions
as the reactants react their concentrations will fall so the forward reaction will slow down. but as more and more products are being made up the concentration will rise and the backward reaction will speed up
32
what is equilibrium
after a while in reversible reactants the forwards reaction will be going at the exactly same rate as the backward reaction
33
what is happening at equilibrium
both reactions are still happening but there is no overall effect which means the concentrations of the reactants and products wont change
34
what is a closed system
that none of the reactants or products can escape and nothing else can get in
35
where does equilibrium have to take place for it to be reached
in a closed system
36
when a reaction is at equilibrium doe sit mean that the amount of reactants and products are equal
no it means the concentrations of the reactants and the products remain constant
37
if the equilibrium lies to the right what does it mean
the concentration of products is greater than the concentration of reactants
38
if the equilibrium lies to the left what does it mean
the concentration of reactants is greater than the concentration of products
39
what are the conditions that affect the position of the equilibrium
- the temperature - the pressure ( only affect equilibrium involving gases) - the concentration of reactants and products
40
in reversible reactions if the reaction is _________ in one direction it will be ___________ in the other
endothermic exothermic
41
What happens in an endothermic reaction?
heat is taken in from the surroundings
42
what does collision theory state
theory states that for particles to react, they have to collide with sufficient energy
43
what does La ch ateliers principle state
if you try to change the conditions of a reversible reaction, the position of the equilibrium will shift to try and counteract the change
44
At equilibrium, if there are more products than reactants, we say that the position of equilibrium lies:
to the right
45
what can la chateliers principle useful for
it can be used to predict the effect of any changes you make to a reaction system
46
in reversible reaction if one direction is exothermic then the other one is
endo thermic
46
2NO2(g) ⇋ N2O4(g) (-24 kJ mol-1) In the reaction above, the (-24 kJ mol-1) tells us that the forward reaction is:
exothermic because it is negitive
47
An increase in pressure moves the position of equilibrium to whichever side has the:
least number of molecules
48
In a reversible reaction, changes in pressure will only affect substances that are in the:
gaseous state
49
What are the three factors that affect the position of equilibrium?
temperature pressure concentration
50
N2(g) + 3H2(g) ⇋ 2NH3(g) In the above reaction, increasing the pressure will:
shift the position of the equilibrium to the right
51
if you decrease the temperature in a reversible reaction the equilibrium will move....
in the exothermic direction to produce more heat. which means you will get more products for the exothermic reaction and less products for the endothermic reaction
52
if you increase the temperature in a reversible reaction the equilibrium will move..
in the endothermic reaction to try and decrease the temperature. which means you ill get more endothermic products and less exothermic products
53
what happens if there is a decrease in pressure in a reversible reaction
the equilibrium will try to increase it and move in the direction with the most molecules of gas
54
what happens if you change the concentration of either of the reactants or products in a reversible reaction
the system will no longer be at equilibrium
55
how does the reaction system respond when you change the concentration in a reversible reaction
when you change the concentration the system will no longer be at equilibrium so they system responds by bringing itself back to equilibrium
56
how does changing the concentration in a reversible reaction affect the amounts of products and reactants produced
if you increase the concentration of reactants the system tries to decrease it by making more products if you decrease the concentration of reactants the system tries to increase it by making more products
57
what are the two ways we can measure the rate of a reaction? | practical
- precpitation and colour change - the volume of gas given off
58
what must the solution be like to do the preciptation and colour chnage practical
the inital solution but be transparent and the product is a precpitate which colouds in the solution
59
what are the steps in the precipitations and colour change practical
- conical flask - 10cm cubed of thiosulfate solution into flask - place the flask over a black cross - put some hydrochloric acid in the flask - swirl solution + start stop watch - look down from the top of the flask - the solution will turn cloudy and stop stopwatch when cross is no longer visable - repeat expierment using different concentration of starting solution
60
what is the problems with the precipitation and colour change experiment how can you reduce this problem?
different people have different eyesight which means some people may be able to see the cross for longer and may not get the same results by giving everyone the same size cross
61
what is the dependant variable | meaning
the variable being measured
62
what is the idependant variable | meaning
the variable being changed
63
what is the control variable
the variable that stays the same
64
what are the steps in the measuring the volume of gas given off practical | measuring rates of reaction
- conical flask with 50cm cubed of hydrochloric acid - attach conical flask to a bung and delivery tube - place end of delivery tubed into a container with water - place upturned measuring cyclinder filled with water over the delivery tube - add 5g of magnesium/ calcium carbonate to acid and start the stop watch - measure volume of gas produced every ten seconds the volume of gas produced in the cylinder - continue until no more hydrogen is given off - repeat experiment using different concentrations of acid/calcium carbonate ( depending on what question asks)
65
how does the precipitation and colour change practical measure the rate of reaction
the quicker the cross takes to disappear the quicker the reaction
66
how does the measuring the volume of gas given off practical measure the rate of reaction
the more gas given off during a time interval, the faster the reaction
67
What is the purpose of the bung and delivery tube in the measuing the volume of gas given off practical
to make sure no gas hydrogen gas escapes
68
What is the purpose of the black paper cross in the precpitation and colour change practical
to provide a reference point for visibility
69
What is the dependent variable in the measuring the volume of gas produced practical
the amount of hydrogen gas produced
70
What is the independent variable in the measuring the volume of gas produced practical
the concentration of hydrochloric acid
71
What is the control variable in the measuring the volume of gas produced practical
the temperature of the reaction
72
what is the result if we increase the concentration of teh hydrochloric acid on the measuring teh volume of gas practical
a higher concentration of acid gives a faster rate of reaction
73
Outline a plan to investigate how the rate of this reaction changed when the concentration of the hydrochloric acid was changed. what will you do to make sure it is a fair test
- remove bung and add magnesium * start stopclock / timer * measure volume of gas at fixed time intervals * repeat with different concentrations of acid * control volume of acid * control initial temperature of acid * control amount of magnesium
74
why does sulfur dioxide have a low boiling point
small molecules with weak intermolecular forces (so) only a small amount of energy is needed to separate the molecules
75
what effect does a catalyst has on the position of the equilibrium.
it will have no affect because it speeds up the forwards reaction and the backwards reaction in the same direction

chem 2 (6 decks)

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