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Chemistry > Topic 7: Rates of Reaction and Energy Changes > Flashcards

Topic 7: Rates of Reaction and Energy Changes Flashcards

(53 cards)

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1
Q

What is the rate of a reaction?

A

Change in product or reactant over time

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2
Q

What is the formula for rate of reaction?

A

Rate = amount of product formed ÷ time

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3
Q

What equipment is used to measure gas volume?

A

Gas syringe

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4
Q

How is a gas syringe used to measure rate?

A

Collect gas produced in syringe and measure volume over time

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5
Q

What equipment is used to measure change in mass?

A

Mass balance

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6
Q

How is a mass balance used to measure rate?

A

Record mass at intervals as gas escapes and mass decreases

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7
Q

How can you investigate how temperature affects rate?

A

Mix sodium thiosulfate and hydrochloric acid in conical flask placed over a black cross then time how long it takes for the cross to disappear at different temperatures

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8
Q

How can you investigate how surface area affects rate?

A

React different sizes of calcium carbonate (powder vs chips) with same volume and concentration of acid and measure gas volume over time with a gas syringe

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9
Q

How can you investigate how concentration affects rate?

A

React same mass of marble chips with acids of different concentrations and measure gas volume over time with syringe

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10
Q

What is collision theory?

A

Particles must collide with enough energy to react

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11
Q

What does ‘enough energy’ mean in collision theory?

A

Particles must meet or exceed the activation energy

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12
Q

How does increasing temperature affect rate?

A

Particles move faster so more frequent collisions and more particles have energy above activation energy

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13
Q

How does increasing concentration affect rate?

A

More particles in same volume so more frequent collisions

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14
Q

How does increasing pressure affect rate (for gases)?

A

Same number of gas particles in smaller volume increases collision frequency

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15
Q

How does increasing surface area affect rate?

A

More exposed particles on solid surface so more frequent collisions

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16
Q

Why does a powder react faster than lumps?

A

Powder has greater surface area to volume ratio so more collisions occur per second

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17
Q

What is a catalyst?

A

Substance that increases reaction rate without being used up

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18
Q

How do catalysts work?

A

They provide an alternative reaction pathway with lower activation energy

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19
Q

What are enzymes?

A

Biological catalysts

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20
Q

What is an example of a catalyst?

A

Iron in the Haber process

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21
Q

What is an example of an enzyme catalyst?

A

Yeast enzyme catalysing alcohol fermentation from sugar

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22
Q

What is an exothermic reaction?

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A

Reaction that releases energy to surroundings

23
Q

What happens to temperature in an exothermic reaction?

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A

Temperature of surroundings increases

24
Q

What happens to energy in exothermic reactions?

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A

Products have less energy than reactants

25
What are examples of exothermic reactions?
Combustion neutralisation respiration freezing condensation
26
What is an endothermic reaction?
Reaction that takes in energy from surroundings
27
What happens to temperature in an endothermic reaction?
Temperature of surroundings decreases
28
What happens to energy in endothermic reactions?
Products have more energy than reactants
29
What are examples of endothermic reactions?
Thermal decomposition photosynthesis melting boiling
30
What is bond energy?
Energy needed to break one mole of a type of bond in a gaseous molecule
31
Is breaking bonds endothermic or exothermic?
Endothermic because energy is taken in
32
Is making bonds endothermic or exothermic?
Exothermic because energy is released
33
What is the rule for total energy change?
Energy change = energy in to break bonds − energy out from making bonds
34
What does a negative energy change mean?
Exothermic reaction
35
What does a positive energy change mean?
Endothermic reaction
36
Why do exothermic reactions give out energy?
More energy is released by making bonds than is used to break them
37
Why do endothermic reactions absorb energy?
More energy is needed to break bonds than is released by forming new ones
38
What is a reaction profile?
Diagram showing energy of reactants and products over time
39
How does an exothermic reaction profile look?
Products lower than reactants with energy released shown downwards
40
How does an endothermic reaction profile look?
Products higher than reactants with energy taken in shown upwards
41
What is activation energy?
Minimum energy required for a reaction to occur
42
Where is activation energy on a profile diagram?
From reactants to the peak of the curve
43
What causes confusion in endothermic reactions?
Energy taken in raises product energy but not temperature because energy is used for bond breaking not heating
44
What causes confusion in exothermic reactions?
Energy released lowers product energy and increases temperature of surroundings not products
45
In endothermic reactions what happens to product energy?
Products have higher energy because more energy was needed to break bonds
46
In exothermic reactions what happens to product energy?
Products have lower energy because more energy released by forming bonds than needed to break them
47
Why does the temperature of products not rise in endothermic reactions?
Energy is used for breaking bonds not increasing kinetic energy
48
Why does the temperature of surroundings rise in exothermic reactions?
Energy released from forming bonds is transferred to surroundings as heat
49
Why does a high bond energy mean a strong bond?
More energy is needed to break it
50
Is bond energy the same as energy stored in the substance?
No bond energy is the energy needed to break the bond not energy stored in molecule
51
In bond energy calculations do we add stored energy?
No we compare total energy used to break and energy released from making bonds
52
What is the temperature of reactants and products in an exothermic reaction?
Temperature of reactants and products increases because energy is released into the surroundings and absorbed by the reaction mixture
53
What is the temperature of reactants and products in an endothermic reaction?
Temperature of reactants and products decreases because energy is absorbed from the surroundings and used for bond breaking not for heating the substances

Chemistry (5 decks)

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