4 Chemical Changes - Electrolysis Flashcards

1
Q

What is electrolysis?

A

Using electricity to break down a substance

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2
Q

What happens to an ionic substance when it is melted or dissolved in water?

A

The ions become free to move around

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3
Q

What is the name for the positive electrode?

A

The anode

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4
Q

What is the name for the negative anode?

A

The cathode

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5
Q

Do positive ions move to the anode or the cathode?

A

Cathode

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6
Q

Do negative ions move to the anode or the cathode?

A

Anode

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7
Q

At which electrode would Zn2+(aq) turn into Zn(s)?

A

Cathode (needs to gain electrons)

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8
Q

At which electrode would Cl-(aq) turn into Cl2(g)?

A

Anode (needs to lose electrons)

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9
Q

Balance the equation: Al3+ + e- gives Al

A

Al3+ + 3e- –> Al

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10
Q

Balance the equation: Cl- gives Cl2 + e-

A

2Cl- –> Cl2 + 2e-

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11
Q

Balance the equation: O2- gives O2 + e-

A

2O2- –> O2 + 4e-

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12
Q

What will be the products for the electrolysis of molten iron bromide?

A

Iron and bromine

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13
Q

What will be the products for the electrolysis of molten zinc oxide?

A

Zinc and oxygen

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14
Q

When is electrolysis used to extract metals from their ores?

A

When the metals are more reactive than carbon, e.g. aluminium

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15
Q

What are the two main disadvantages of using electrolysis to extract metals?

A

Requires a large amount of energy to melt the compounds and to produce the necessary electricity

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16
Q

Why is aluminium oxide mixed with cryolite when extracting aluminium?

A

To lower the melting point from 0ver 2000 degrees celsius down to 900 degrees celsius

17
Q

What is produced at the anode and cathode in the electrolysis of aluminium oxide?

A

Aluminium at the cathode and oxygen at the anode

18
Q

Why does the anode need to be replaced in the electrolysis of aluminium oxide?

A

The carbon anode is non-inert (reactive). The oxygen reacts with the is to produce carbon dioxide.

19
Q

In the electrolysis of sodium chloride solution, what are the products?

A

Chlorine gas and hydrogen gas

20
Q

Why is sodium not produced in the electrolysis of sodium chloride solution?

A

It is more reactive than hydrogen so hydrogen is produced instead.

21
Q

What is produced at the anode in electrolysis of solutions?

A

Either a halogen or oxygen (when there is no halogen present)