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Chemistry Paper 2 > The Rate And Extent Of Chemical Change > Flashcards

The Rate And Extent Of Chemical Change Flashcards

1
Q

What is the rate of reaction?

A

How fast the reactants are changed into products.

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2
Q

What is an example of a slow reaction?

A

Rusting

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3
Q

What is an example of a medium reaction?

A

Magnesium reacting with acid

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4
Q

What is an example of a fast reaction?

A

Explosions

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5
Q

When do chemical reactions occur?

A

When particles of reactants collide with enough energy to react.

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6
Q

What is the energy required for a successful reaction called?

A

The activation energy

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7
Q

What is the activation energy (Ea)?

A

The minimum amount of energy that particles must have in order to react.

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8
Q

What is collision theory?

A

During any reaction, the reactants must bump into each other in order to react and make a product. These bumps are called collisions. Either the reactants can collide and just bump into each other, or, if they bump with enough energy a product is formed.

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9
Q

What factors affect the rate of reaction?

A

Temperature
Concentration (solutions)/ pressure (gases)
Surface area
Catalysts

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10
Q

How does an increase in temperature increase the rate of reaction?

A

When the temperature is increased, the particles move faster. If they’re moving faster, they’re going more frequently. The faster they move, the more energy they have so more of the collisions will have enough energy to make the reaction happen.

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11
Q

How does an increase in concentration/ pressure increase the rate of reaction?

A

If a solution is more concentrated, it means there are more particles knocking about in the same volume of water (or another solvent). When pressure of a gas increases, the same number of particles occupied a smaller space. This makes collisions between reactant particles more frequent.

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12
Q

How does an increase in surface area increase the rate of reaction?

A

If one of the reactants is a solid, then breaking them up into smaller pieces will increase its surface area to volume ratio. This means that for the same volume of the solid, the particles around it will have more area to work on- so they’re be more frequent collisions.

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13
Q

How do catalysts affect the rate of reaction?

A

A catalyst is a substance that speeds up a reaction without being used up in the reaction itself. This means its not part of the overall reaction equation. Different catalysts are needed for different reactions, but they all work by decreasing the activation energy needed for the reaction to occur. They do this by providing an alternative reaction pathway with a lower activation energy.

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14
Q

How can the rate of reaction be observed?

A

By how quickly the reactants are used up or how quickly the products are formed.

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15
Q

How do you calculate the mean rate of reaction?

A

Amount of reactant used or product formed/ time

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16
Q

If the product or reactant is a gas what do you measure it in?

A

Cm3 and if the time is in seconds cm3/s.

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17
Q

If the product or reactant is a solid what do you measure it in?

A

g

Mol/s

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18
Q

What are the 3 ways of measuring the rate of reaction?

A

Precipitation and colour change.
Change in mass.
Volume of gas given off.

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19
Q

What can you use to see a visual change in a reaction?

A

The initial solution is transparent and the reactant is a precipitate which clouds in water.

20
Q

How do you observe the rate of a reaction?

A

You can observe a mark through the solution and measure how long it takes for it to disappear, the faster the mark disappears, the quicker the reaction.
Tip- if products are coloured and the reactants are colourless (or vice versa) you can time how long it takes for the solution to lose (or gain) its colour.

21
Q

How do you measure the rate of reaction by observing a change in mass?

A

As gas is released, the mass disappearing is measured on a balance, the quicker the reading on the balance drops, the faster the reaction

22
Q

How do you measure the rate of reaction by a volume of gas given off?

A

Involves a gas syringe, more gas given off at a time interval, the faster the reaction.

23
Q

What is the method for the rate experiment for the reaction of magnesium and HCL to produce H2 gas?

A

1) Add a set volume of dilute hydrochloric acid to a conical flask.
2) Add some magnesium ribbon the the acid and quickly attach an empty gas syringe to the flask.
3) Start the stopwatch and take the readings of the volume of gas in the gas syringe at regular intervals.

24
Q

What is the method for the rate experiment for the effect of using different acid concentration?

A

Repeat the experiment for the magnesium and HCL one with a number of different concentrations of acid.

25
Q

What is the method for the rate experiment for sodium Thiosulfate and HCL producing a cloudy precipitate?

A

1) Add a set volume of dilute sodium thiosulfate to a conical flask.
2) Place the flask on a piece of paper with a black cross drawn on it.
3) Add some dilute HCL to the flask and start the stopwatch.
4) Watch the black cross disappear.

26
Q

What is the method for the rate experiment for how the concentration of acid affects the rate?

A

1) the reaction can be repeated with solutions of either reactant at different concentrations.
2) These results show the effect of increasing the concentration of HCL in the rate of reaction, when added to an excess of sodium Thiosulfate.
3) higher the concentration, the quicker the reaction.

27
Q

How do you find the mean rate of reaction from a graph?

A

Change in y/ change in x

28
Q

How do you draw a tangent?

A

1) position a ruler at where you want to find the rate.
2) Adjust the ruler until the space between the ruler and the curved is equal in both sides of the point.
3) Draw along the rule to make the tangent.
4) pick two points in the line that is easy to read, use them to find the gradient of the tangent.

29
Q

What happens in terms of concentration as reactants react?

A

The forward one will slow down.

30
Q

What happens when more concentration is added to the reaction?

A

The backward reaction will speed up.

31
Q

What happens to a reaction after a while?

A

The forward and backward reaction will he going at exactly the same rate- they are at equilibrium.

32
Q

What does it mean that the reactions are at dynamic equilibrium?

A

Both reactions are happening but there’s no overall effect.

33
Q

What do the circumstances have to be for a reaction to get to dynamic equilibrium?

A

If the reversible reaction takes place in a closed system- nothing can escape/ get in.

34
Q

Are the amounts of products and reactants equal when the reaction’s at equilibrium?

A

No

35
Q

If the equilibrium lies to the right…

A

The concentration of the products is greater.

36
Q

If the equilibrium lies to the left…

A

The concentration of the reactants is greater.

37
Q

If the reaction is exothermic in one way…

A

It will be endothermic in the other way.

The energy transferred from the surroundings is equal to the energy transferred to the surroundings.

38
Q

What is an example of a reversible reaction?

A

If you heat blue hydrated copper (ll) solfataras crystals, it drives the water off and leaves white anhydrous copper (ll) sulfur powder- endothermic.

If you add some water it turns to the blue crystals again- exothermic.

39
Q

What is Le Chatlier’s principle?

A

That is you change the conditions of a reversible reaction, the system will counteract that change.

40
Q

What can Le Chatlier’s principle be used to predict?

A

The effect of any changes you make to a reaction system.

41
Q

How does a decrease temperature affect the reversible reaction?

A

If you decrease the temperature, the equilibrium will move to the exothermic direction to produce more heat. You’ll get more products for the exothermic and less for the endothermic.

42
Q

How does an increase in temperature affect the reversible reaction?

A

The equilibrium will move to the endothermic direction and try to decrease it. More products for endothermic and less for exothermic.

43
Q

How does an increase in pressure affect the reversible reaction?

A

The equilibrium tries to decrease it, moves to a direction where there are fewer molecules of gas.

44
Q

How does a decrease in pressure affect a reversible reaction?

A

The equilibrium tries to increase it, moves to a direction where there are more molecules of gas.

45
Q

What happens if you increase the concentration of a reversible reaction?

A

The system tries to reduce it by making more products.

46
Q

What happens if you decrease the concentration of a reversible reaction?

A

The system tries to increase by reducing the amounts of reactants.

47
Q

What happens if you change the concentration for reactants or products?

A

System will no longer be at equilibrium.

Chemistry Paper 2 (1 decks)

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