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Chemistry AQA > C-6 The rate and extent of chemical change > Flashcards

C-6 The rate and extent of chemical change Flashcards

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1
Q
  • What is the the rate of reaction
A
  • How fast the reactants are changed in products
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2
Q
  • what are the equations used to calculate rate of reaction
A

mean rate of reaction =

quantity of reaction used//time taken

Sanity ion product formed// time taken

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3
Q

What must happen in order for a reaction to take place

A
  • Must collide with enough energy

-

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4
Q

What is collision theory

A
  • The more collisions there are the faster the rate of reaction
  • the energy transferred during a collision. Particles have to collide with enough energy for the collision to be successful
  • Activation energy- the amount of energy needed to break to bonds
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5
Q

What increases the rate of reaction on a theory basis

A
  • More collisions increase the rate of reactions
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6
Q

How does temperature effect the rate of reaction

A
  • When temperature increase the kinetic energy store increases and they move faster
  • As they are moving faster they will collide more frequently
  • The faster they move the more energy they gave so more collisions will have enough energy to make the reaction happen
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7
Q

What effect does concentration and pressure have on a reaction

A
  • IF a solution is more concentrated it means there are more particles knocking about in the same volume of water
  • Similarly when pressure increases it means same number of particles occupy smaller space
  • makes collisions more frequent- therefore rate of reaction increases.
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8
Q

What effect does surface area have on rate of reaction

A
  • IF reactants is solid then breaking it up will increase surface area to volume ratio
  • This means that for the same volume of solid particles will have more area to work on- so reactions will be more frequent
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9
Q
  • What is a catalyst
A
  • Substance that speeds up a reaction without being used up itself within the reaction - not part of overall equation
    • Different catalysts are needed for different reactions- but they all decrease activation energy- provide an alternate pathway- lower energy needed
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10
Q
  • How do catalysts effect the rate of reaction
A
  • Different catalysts are needed for different reactions- but they all decrease activation energy- provide an alternate pathway- lower energy needed
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11
Q
  • What are enzymes
A
  • Biological catalysts - speed up rate of reaction in living things
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12
Q
  • What are the steps in measuring change in rate of reaction
A
  • Colour change and precipitation
  • Change in mass- gas
  • Volume of gas given off
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13
Q

How do you investigate rat elf rate of reaction in precipitation and colour

A
  • Visual change
  • Observe a mark through solution and see how ;omg to tales to disappear- faster it takes faster rate
  • If reactants are coloured and products colourless you can see how long it takes to gain or loose colour
  • Subjective results
  • Cant plot
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14
Q

How do you investigate rate of reaction using change in mass

A
  • measuring speed that produces a gas
  • As gas is related the mass leaving is measured in change in mass balance
  • IF take measurements at regular intervals a graph can be plotted
  • Most accurate- gas goes into room
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15
Q
  • How do you investigate rate of reaction using gas syringe
A
  • Gas given off
  • More gas given off means faster rate
  • nearest cm 3
  • Graph
  • Can low plunger out
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16
Q

What is the two rates experiments method

A
  • Add set volume of HCL to conical flask
  • Add magnesium while on a mass balance
  • Record mass change at set intervals
  • Test with other concentrations
  • Plot on same graph and compare
17
Q
  • What is is the black cross test
A
  • Both clear- go yellow
  • Add set amount of sodium
  • Place piece of paper in
  • Test time to no longer see black cross for different concentrations
  • No graph
18
Q
  • How can you calculate mean rate of reaction
A
  • Overall change//overall time
19
Q
  • How do you find rate of reaction at a particular point
A
  • Draw a tangent and find relative gradient
20
Q
  • What are reversible reaction
A
  • In some chemical reactions the products can react to produce original reactants
21
Q
  • How can reversal reactions be represented
A
  • A + B <=> C + D
22
Q
  • How can the direction of reversible reactions be change
A
  • By changing the conditions
    e. g Ammonium chloride <====> Ammonium+ hydrogen

to move left to right - heat
to remove left to right- cool

23
Q
  • What are the energy changes in a reversible reaction
A
  • A reversible reaction is endothermic in one direction and exothermic in another. Same amount of energy transferred
24
Q
  • What is an example of exothermic and endothermic reversible reactions
A
  • Hydrated copper sulfate <=====> Anhydrous copper sulfate+ water

Left to right- endothermic
Right to left- exothermic

25
Q

What is an equilibrium

A
  • When a reversible reaction occurs in apparatus that prevents the escape of reactants and products
26
Q

When is equilibrium reached

A

Equilibrium is reached when the forward and reverse reactions occur at exactly the same rate

27
Q

What do the relative amounts of reactants and products depend on in an equilibrium

A
  • The conditions
28
Q

What happens if there is a change to a system that is in equilibrium

A
  • The system responds to correct it

- La chandelier’s principle

29
Q

How does a system respond to temperature change

A
  • All reactions are endothermic one way and exothermic another
  • IF you decrease the temperature- equilibrium will move towards the exothermic in order increase the temperature- more products for endothermic- less for exothermic
  • IF you Increase the temperature the equilibrium will move towards endothermic in order to decrease the temperature. More products for Endothermic. Less for Exothermic
30
Q

How does a system respond to a pressure change

A
  • Only relevant for gases
  • IF pressure is increased to try and reduce it it moves towards state where less molecules are present
  • If pressure is decreased it will move towards state where more molecules re present
31
Q
  • How does a system respond to concentration increase
A
  • If you increase concentration it will no longer be at equilibrium
  • System attempt to bring it back
  • IF increase in concentration of reactions- shift towards products
  • If increase in products- shift toward reactants

Chemistry AQA (10 decks)

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