Unit5 Flashcards

1
Q

What is an exothermic energy transfer?

A

transfer to the surroundings

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2
Q

What is an endothermic energy transfer?

A

transfer from the surroundings

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3
Q

What is a reaction profile?

A

diagram showing how the energy changes in a reaction

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4
Q

What is the activation energy?

A

minimum amount of energy required before a collision will result in a reaction

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5
Q

What is bond energy?

A

the energy required to break a bond or the energy released when a bond is formed

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6
Q

In terms of bond breaking and making, what is an exothermic reaction?

A

less energy is required to break the bonds than is released when making the bonds

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7
Q

In terms of bond breaking and making, what is an endothermic reaction?

A

more energy is required to break the bonds than is released when making the bonds

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8
Q

What is a battery?

A

two or more chemical cells connected in series

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9
Q

How does the potential difference of a cell depend on the metals that the electrodes are made of?

A

the bigger the difference in reactivity, the greater the potential difference

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10
Q

How can some cells be recharged?

A

by applying an external current

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11
Q

Why can some cells not be recharged?

A

the reaction cannot be reversed

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12
Q

What is a fuel cell?

A

cell that uses a fuel and oxygen to generate electricity

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13
Q

In the hydrogen fuel cell, what is the overall reaction?

A

2H2(g) + O2(g) ➞ 2H2O(l)

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14
Q

In the alkaline hydrogen fuel cells, what are the half equations?

A

2H2(g) + 4OH−(aq) ➞ 4H2O(l) + 4e− O2(g) + 2H2O(l) + 4e− ➞ 4OH−(aq)

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15
Q

Give an advantage of the hydrogen fuel cell.

A

only product is water, do not need to be electrically recharged

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16
Q

Give a disadvantage of the hydrogen fuel cell.

A

hydrogen is flammable, difficult to store and is often produced from non-renewable sources

17
Q

How are chemical cells made?

A

connect two different metals (electrodes) in a solution (electrolyte)