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chemistry > electrolysis > Flashcards

electrolysis Flashcards

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1
Q

definition of electrolysis

A

using electricity to split ionic compounds

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2
Q

main uses of electrolysis

A

-extraction of metals
-make chlorine gas
-make hydrogen gas
-making soap

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3
Q

why must the compound be molten or dissolved?

A

These compounds are called electrolytes. The ions are free to move/ carry charge, therefore they can conduct electricity.

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4
Q

What happens at the electrodes?

A

Ions are DISCHARGED, turning into uncharged ions.

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5
Q

What must happen for an anion (negative electron) to be discharged?

A

The anion must LOOSE electrons = oxidation

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6
Q

What must happen for a cation (positive electron) to be discharged?

A

The cation must GAIN electrons = reduction

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7
Q

Which ion is attracted to the anode?

A

The ANION is attracted to the anode, the POSITIVE electrode

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8
Q

Which ion is attracted to the cathode?

A

The CATION is attracted to the cathode, the NEGATIVE electrode.

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9
Q

Why are these ions attracted to these electrodes?

A

Because opposite charges attract!

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10
Q

Why is there a cell and bulb in the circuit?

A

Cell- source of electrical current
Bulb- confirms electrical conductivity throughout circuit.

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11
Q

When electrolysing magnesium chloride, positive Mg2+ ions attract to the cathode. What process takes place and why and what is deposited?

A

-Reduction takes place
-a solid metal deposits, forming around the cathode.
-because magnesium is a metal

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12
Q

When electrolysing magnesium chloride, negative Cl- ions attract to the anode. What process takes place and why and what is deposited?

A

-Oxidation takes place
-this must happen to TWO Cl- ions as halogens must form diatomic molecules
-as Cl2 is a gas, we will see effervescence around the anode

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13
Q

Half equation for magnesium

A

Mg2+ + 2e- = Mg

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14
Q

Half equation for chlorine

A

Cl2 + 2e- = 2Cl-

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15
Q

Half equation for sodium

A

Na+ + e- = Na

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16
Q

Half equation for bromine

A

Br2 + 2e- = 2Br-

17
Q

Half equation for zinc

A

Zn2+ + 2e- = Zn

18
Q

Half equation for hydrogen

A

2H+ + 2e- = H2

19
Q

Half equation for hydroxide

A

4OH- = 2H2O + O2 + 4e-

20
Q

What is the electrolyte?

A

The substance broken down that is electrically conductive.

21
Q

What’s the advantage of aqueous over molten?

A

It uses less energy, however we get different products

22
Q

During aqueous electrolysis, there are always what present?

A

-Hydrogen ions (H+)
-Hydroxide ions (OH-)

23
Q

Why are these ions present in aqueous electrolysis?

A

Because the water splits under the current

24
Q

Aqueous electrolysis - Cathode
The positive cation that will form the ??? reactive product is discharged. If a metal, ???. If hydrogen, then ???

A

-Least reactive
-If a metal, then solid metal will deposit
-If hydrogen, then hydrogen gas will effervescence

25
Q

Aqueous electrolysis - Anode
If one of the negative anions is a ??? it will be discharged, its ??? gas will ???

A

-Halide
-Halogen
-Effervescence

26
Q

Aqueous electrolysis - Anode
If neither of the negative anions are a halide, ??? is discharged to form ??? and will ???

A

-Hydroxide
-Oxygen gas
-Effervescence

27
Q

Observations of the electrolysis of copper chloride - Cathode (negative electrode)

A

-bubbles of gas
-bleached blue litmus paper
-chlorine gas (chlorine is a halogen, so it is a product)

28
Q

Observations of the electrolysis of copper chloride - Anode (positive electrode)

A

-orange/brown solid metal deposit
-copper atoms
-solution will become paler (from blue) until it turns COLOURLESS

29
Q

What is the test for oxygen?

A

If a glowing splint relights, oxygen is therefore present.

30
Q

When Brine is electrolysed, what is produced?

A

-Hydrogen
-Chlorine
-Sodium hydroxide

chemistry (1 decks)

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