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Chemistry ⚗ > ✅ > Flashcards

✅ Flashcards

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1
Q

What is an exothermic reaction?

A

A reaction that transfers heat from the chemicals to the surroundings

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2
Q

What is an endothermic reaction?

A

Reactions that take in heat from the surroundings

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3
Q

Examples of exothermic reactions

A

Burning fuels

Neutralisation

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4
Q

Examples of endothermic reactions

A

Electrolysis
Thermal decomposition
Eating sherbet

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5
Q

If you felt a container where a endothermic reaction was happening, what would you feel?

A

The surroundings and the mixture would feel colder

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6
Q

If a reversible reaction is endothermic in the forward direction

A

It is exothermic in reverse

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7
Q

Bond breaking is

A

Endothermic

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8
Q

Bond making is

A

Exothermic

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9
Q

Examples of products using exothermic reactions

A

Hand warmers

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10
Q

Uses of endothermic reactions

A

Ice packs

Chill cans of drinks

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11
Q

How do ice packs work?

A

It contains ammonium nitrate, which absorbs energy from its surroundings so they cool down

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12
Q

How do hand warmers work?

A

Iron rusts, catalysed by salt, which provides heat

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13
Q

What are the products if a reaction measured in?

A

kJ/mol

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14
Q

What does the reaction profile for an exothermic reaction look like?

A

The reactants start at a higher energy level than the products as energy is released

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15
Q

Why does an exothermic reaction heat up?

A

An equal amount of energy is transferred to the surroundings as is in the reaction and this energy is often heat

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16
Q

What would the reaction profile for an endothermic reaction look like?

A

The reactants start at a lower level than the products because energy is absorbed from the surroundings

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17
Q

What happens to the temperature of an endothermic reaction?

A

The surroundings get colder because energy is absorbed by the reaction

18
Q

What is the activation energy?

A

The minimum amount of energy needed to start a reaction

19
Q

How to see the activation energy on a reaction profile

A

The energy difference between the reactants and the peak of the curve

20
Q

What type of process is bond breaking and why

A

Endothermic, energy has to be supplied to overcome the bonds

21
Q

What type of process is bond making and whh

A

Exothermic, when bonds are formed, energy is released

22
Q

How to remember bond making and breaking process

A

Breaking bonds aBsorbs energy, foRming bonds Releases energy

23
Q

How to find how much energy is taken in or released?

A

Difference between reactants and products

24
Q

What makes a reaction exothermic in terms of bonds?

A

When the energy released when new bonds are made is more than the energy needed to break them, so it is transferred to surroundings

25
Q

What makes a reaction endothermic in terms of bonds?

A

When the energy needed to break the bonds in the reactants is more than the energy formed, so energy needs to be absorbed

26
Q

What is bond energy?

A

The energy needed to break the bond between two atoms

27
Q

How to calculate bond energies

A

1) find out how much energy is needed to break bonds in reactants
2) how much energy is released when new bonds are formed

28
Q

When a bond is broken or formed, what is the same always?

A

The amount of energy needed to make/break it

29
Q

what is the bond energy of a bond?

A

the amount of energy needed to break it

30
Q

what is it called when more energy is needed to break bonds than make bonds

A

endothermic

31
Q

what is it called when more energy is needed to make bonds than break them

A

exothermic

32
Q

what is the energy released?

A

difference between reactants and products

33
Q

how to tell what the voltage of a battery will be

A

the greater the difference in reactivity between the two elements, the higher the voltage

34
Q

when there are two metals in a cell, what happens to the electrons?

A

the most reactive donates them to the least reactive

35
Q

how does a simple cell work?

A

the more reactive metal donates electrons to the least reactive and this carries the charge

36
Q

what is a fuell cell?

A

a cell supplied by a fuel and oxygen

37
Q

how does a fuel cell work?

A

the fuel becomes oxidised and sets up a voltage

38
Q

in a fuel cell, what happens to the electrodes?

A

they switch (cathode = positive)

39
Q

in a hydrogen-oxygen fuel cell, what happens?

A

hydrogen loses electrons to produce H+ ions
oxygen gains electrons to make O2
These combine to form water

40
Q

Why is hydrogen useful as a fuel?

A

When it reacts with oxygen, more energy is released in bond breaking than bond making so it is exothermic

Chemistry ⚗ (17 decks)

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