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Chemistry Paper 2 > Rates of Reaction and Energy changes > Flashcards

Rates of Reaction and Energy changes Flashcards

1
Q

What is the rate of reaction?

A

How quickly a reaction happens.

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2
Q

How can the rate of reaction be observed?

A

Either by measuring how quickly the reactants are used up or how quickly the products are formed.

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3
Q

What is the formula for Average rate of reaction?

A

Amount of reactant used or amount of product formed/Time

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4
Q

What are the 3 different ways the rate of reaction can be measured?

A

Precipitation, Change in mass or Volume of gas given off.

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5
Q

Explain how the precipitation method works?

A

Works for any reaction where mixing two see-through solutions produces a precipitate, which clouds the solution.

Mix the two reactant solutions and put the flask on a piece of paper that has a mark on it.
Observe the mark through the mixture and measure how long it takes for the mark to be covered.

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6
Q

The faster the mark disappears…

(Precipitation method)

A

the faster the reaction.

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7
Q

Explain how the Change in mass method works?

A

You can measure the rate of reaction that produces a gas using a mass balance.
As the gas is released, the lost mass is easily measured on the balance.

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8
Q

How do you know when the reaction has finished?

(Change in mass method)

A

The reading on the balance stops changing.

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8
Q

The quicker the reading on the balance drops…

(Change in mass method)

A

the faster the reaction.

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8
Q

How can rate of reaction be measured by Volume of gas given off?

A

Involves the use of a gas syringe to measure the volume of gas given off.

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9
Q

The more gas given off during a set time interval…

(Volume of gas given off)

A

the faster the reaction.

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10
Q

How can you tell the reaction has finished?

(Volume of gas given off)

A

When no more gas is produced.

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11
Q

How do you calculate rate of reaction?

A

Product made/time OR
Reactant lost/time.

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12
Q

How would you calculate the Mean rate of reaction after a certain amount of time from a graph?

A

Find out the total volume of gas produced after the certain amount of time.
The substitute the values into the equation:
Mean rate of reaction = quantity of product formed/time.

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13
Q

How would you calculate the Actual rate of reaction at a specified time from a graph?

A

Draw a tangent to the curve at the specified time.
Construct a right angled triangle.
Calculate the gradient of the tangent using the equation:
Gradient = Change in Y/ Change in X.

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14
Q

What does the rate of a chemical reaction depend on?

(Collision Theory)

A

How often reacting particles collide.
The energy transferred during a collision.

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15
Q

The more successful collisions there are…

A

the faster the reaction is.

16
Q

What is the Activation energy?

A

The minimum energy that particles need to react when they collide.
Particles need to collide with at least the activation energy for the collision to be successful.

17
Q

Why does increasing the temperature quicken rate of reaction?

A

The particles move faster to have a higher chance of more collisions.
Particles have more energy so collide harder.

18
Q

Why does increasing the concentration of a liquid quicken rate of reaction?

A

There are more liquid particles closer to each other increasing chance of collisions.

19
Q

Why does increasing the pressure on gas particles quicken rate of reaction?

A

The particles are in a smaller volume so are more likely to collide.

20
Q

Why does increasing the surface area of a solid quicken rate of reaction?

A

More solid area is exposed for more chance of collisions.

21
Q

What is a Catalyst?

A

A substance which increases the rate of reaction without being chemically changed or used up in the reaction.

22
Q

How do Catalysts lower activation energy?

A

Looking for a different pathway for the reaction, making it easier to break the old bonds.

23
Q

What is an Exothermic reaction?

A

One which gives out energy to the surroundings, making the temperature rise.

24
Q

What is an Endothermic reaction?

A

One which takes in energy from surroundings, making the temperature fall.

25
Q

What does a Thermometer do?

A

Measure temp before and after.

26
Q

What does a lid do?

A

Insulator that reduces energy transfer out.

27
Q

What does a polystyrene cup do?

A

Insulator that reduces energy transfer out.

28
Q

What does cotton wool do?

A

Reduce energy transfer to the beaker.

29
Q

How can you measure the temperature change when dissolving salts in water?

A

By adding the salt to a polystyrene cup of water and measuring the change in temperature when the salt has dissolved.

30
Q

What happens in a neutralisation reaction?

A

An acid and a base react to form a salt and water.

31
Q

What happens in a displacement reaction?

A

A more reactive element displaces a less reactive element in a compound.
Energy is released in these reactions so they’re exothermic.

32
Q

What happens in a precipitation reaction?

A

When precipitates are formed by two solutions mixing together. Exothermic reactions.

33
Q

Bond breaking is an… exothermic/endothermic process.

A

Endothermic process.

34
Q

Bond formation is an exothermic/endothermic process.

A

Exothermic process.

35
Q

In endothermic reactions, the energy used to break bonds is greater than…

A

the energy released by forming them.

36
Q

In exothermic reactions, the energy released to form bonds is greater than…

A

the energy used to break the bonds.

37
Q

What is the formula for Overall energy change?

A

Energy required to break bonds - Energy released by forming bonds.

38
Q

A positive energy change means…

A

an endothermic reaction.

39
Q

A negative energy change means…

A

an exothermic reaction.

Chemistry Paper 2 (2 decks)

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