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Chemistry > Chemical Changes > Flashcards

Chemical Changes Flashcards

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1
Q

What is Oxidation simple?

A

A reaction were oxygen is added to an element of a compound

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2
Q

What is reduction simple?

A

A reaction where oxygen is removed from an element of a compound

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3
Q

Example of an oxidation reaction

A

2Cu + O2 –> 2CuO

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4
Q

Example of a reduction reaction

A

ZnO + C –> Zn + CO

Zinc atom reduced, Carbon atom oxidised

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5
Q

What is the reactivity series?

A

A series of metals and some non-metals determining their ranks in reactivity

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6
Q

State the reactivity series -

A

Potassium, sodium, lithium, calcium, magnesium, aluminium, carbon, zinc, iron, tin, lead, hydrogen, copper, silver, gold

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7
Q

What is the mnemonic for the reactivity series?

A

Please Stop Loudly Calling Me A Careless Zebra Instead Try Learning How Copper Saves Gold

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8
Q

Why are carbon and hydrogen on the reactivity series?

A

They are very useful in extracting metals from their oxides by reduction processes

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9
Q

Which metals react with water?

A

Metals ABOVE HYDROGEN in the reactivity series react with water, eg.

Ca + 2H2O –> Ca(OH)2 + H2

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10
Q

What happens when acids and metals react?

A

The metal atom REPLACES the hydrogen atom in the acid to produce a salt and a hydrogen gas, eg.

Fe + 2HCl –> FeCl2 + H2

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11
Q

What determines the reactivity of the metal?

A

Its tendency to form ions, (ie. lose electrons)

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12
Q

How can carbon be used as a reducing agent?

A

To remove oxygen from metal oxide ores.

By placing carbon in the reactivity series, it allows us to see whether a metal oxide can be reduced or not by carbon

Metals BELOW carbon in the reactivity series can be extracted by heating the OXIDE with CARBON

Metals HIGHER than carbon have to me extracted by other methods, such as ELECTROLYSIS

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13
Q

How does the displacement of the reactivity series work?

A

A more reactive substance will DISPLACE a less reactive substance from its compounds, eg.

Zn + CuO –> ZnO + Cu

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14
Q

How can we visually see what displacement looks like?

A

New compounds of different metals often have different colours, eg.

Mg + CuSO4 –> MgSO4 + Cu

The blue colour of the CuSO4 FADES as the Mg displaces the Cu from the compound, to make a colourless MgSO4 solution + Cu

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15
Q

How can oxidation and reduction be represented in terms of their ELECTRONS?

A

Through ionic equations and HALF EQUATIONS

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16
Q

What happens when an electric current is passed through a molten ionic compound or aqueous solutions of ionic compounds?

A

The compound decomposes or breaks down into simpler structures

17
Q

What are electrolytes?

A

Liquids and solutions that are able to conduct electricity

18
Q

What is an electrolytic cell?

A

The set-up of the equipment for electrolysis. The equipment is as follows -

  • Electrode
  • Electrolyte
  • Anode
  • Anion
  • Cathode
  • Cation
19
Q

What is an electrode?

A

A rod of metal or graphite through which an electric current flows into or out of an electrolyte

20
Q

What is the electrolyte?

A

An ionic compound in a molten or dissolved solution that conducts the electricity

21
Q

What is an anode?

A

The positive electrode of an electrolysis cell

22
Q

What is the cathode?

A

The negative electrode of an electrolysis cell

23
Q

What is an anion?

A

The negative ions which is attracted to the anode

24
Q

What is a cation?

A

The positively charged ions which are attracted to the cathode

25
Q

Why can’t ionic compounds in a solid state conduct elecricity?

A

They have no free ions that can move and carry the charge. Therefore an ionic compounds must be in a molten state or dissolved in a solution so the charge can pass through

26
Q

What happens when the electrolytic cell is turned on?

A

An electric current is passed through an electrolyte, and the ions in the solution start to move towards the electrodes

27
Q

What is produced at the anode?

A

The NON-METAL

28
Q

What is produced at the cathode?

A

The METAL

29
Q

What are the downsides of electrolysis?

A

Very expensive to provide the large amounts of energy to melt the ores and produce the electrical current

30
Q

How is aluminium extracted from bauxite?

A

Bauxite is purified to produce aluminium oxide

Al2O3 has a very high melting point so it is first dissolved in molten cryolite producing an electrolyte with a lower melting point and a better conductor of electricity - THIS SAVES ENERGY AND MONEY AND MAKES THE PROCESS MORE EFFICIENT

The electrolyte is the solution of aluminium oxide in molten cryolite at a temperature of about 1000°C

Fresh aluminium oxide is added to the cell, where it operates at 5-6 volts and with a current of 100,000 amps

The heat generated by the huge current keeps the electrolyte molten

Oxygen is produced at the cathode, and sometimes reacts with graphite, (carbon) electrode to produce CO2 gas, meaning the carbon anode burns away, so they must be replaced regularly.

The molten aluminium sinks to the bottom of the cell and is gathered at the end of the extraction

31
Q

What happens to water molecules during electrolysis of an aqueous solution?

A

Water molecules DISSOCIATE, producing H+ ions and OH- ions

32
Q

During electrolysis of an aqueous solution, what goes to the anode?

A

Negatively charged OH- ions and negative non-metal ions

33
Q

What is discharged at the anode?

A

Oxygen gas will be produced unless the ionic compound contains HALIDE IONS in which case the HALOGEN will be produced

34
Q

What happens at the cathode during electrolysis of an aqueous solution?

A

Positively charged H+ ions and metal ions are attracted to the cathode but only one will gain electrons. Either HYDROGEN GAS or the METAL will be produced.

If the metal is ABOVE HYDROGEN in the reactivity series, then HYDROGEN WILL BE PRODUCED and bubbling will be seen at the cathode - this is because the more reactive ions will remain in solution, causing the least reactive ion to be discharged.

If the metal is BELOW hydrogen in the reactivity series, then the METAL is produced

35
Q

REQUIRED PRACTICAL

A

TING

36
Q

What do half equations represent?

A

The loss or gain of electrons within substances

37
Q

How can we create ionic equations from half equations?

A

By combining the half equations and cancelling out the electrons

Chemistry (28 decks)

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