&ionic&liquids& - co-op academy failsworth - · pdf file ·...

06/05/15

Ionic Liquids

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All State the forms in

which an ionic compound can conduct electricity

Describe how ionic compounds conduct electricity

Use ionic equaBons to show how ions form

STARTER: Draw the diagram of an ionic laHce structure. Explain why the ions cannot move around.

Ions Revision

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Ions Revision

•  For the following atoms, describe how they form the corresponding ions

a)  Ag à Ag+

b)  Mg à Mg2+

c)  F à F-‐

d)  N à N3-‐

•  Extension: If you feel confident, predict what ions the following atoms will form using their electronic structure or posiBon in periodic table a)  Ca b)  Cl c)  K

EXAMPLE: Na (sodium) atoms forms a Na+ ion by losing 1 electron

Ionic EquaBons •  We can write the loss or gain of electrons as an

equaBon like this:

Sodium atoms (Na) lose 1 electron to become a sodium ion (Na+)

Na à Na+ + e-‐

Copper atoms lose 2 electrons to become copper ions

Cu à Cu2+ + 2e-‐ Some

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Ionic Liquids

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Copy and complete using the words in green:

When a _______ ionic compound ________ in water, the ___________ breaks up. The ions ________ and are free to move around rapidly. The ions can carry electrical _______ through the _________. The soluBon therefore conducts electricity.

WORDS: separate dissolves laHce soluble soluBon charge

Extension: Draw a diagram to show how the soluBon would differ if it were more concentrated

Progress check •  Can you answer the following quesBons?

GRADE: C B A

Extension: Water is made up of covalent molecules. Does it conduct? Why is it not safe to have near electrical equipment?

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Starter Water is made up of covalent molecules. Does it conduct? Why is it not safe to have near electrical equipment?

Electrolyte – ionic liquid or soluBon broken down by electrolysis.

Electrolysis ‘spliHng up compounds using electricity’

Electrode – rod that conducts electricity – come in pairs – one negaBve and one posiBve.

Opposites acract

Electrode – rod that conducts electricity – oden made of graphite or plaBnum – they are inert.

NegaBve ions move to the posiBve electrode e.g. chloride.

PosiBve ions move to the negaBve electrode e.g. copper.

Don’t PANIC - Positive is Anode, Negative Is Cathode.

What did we see happening yesterday?

Salt Anode (+) Cathode (-‐) Potassium Bromide

Aluminium Oxide

Barium Iodide

Sodium Chloride

Calcium Fluoride

List the products of the electrolysis of these molten salts.

Salt Anode (+) Cathode (-‐) Potassium Bromide Bromine Potassium

Aluminium Oxide Oxygen Aluminium

Barium Iodide Iodine Barium

Sodium Chloride Chlorine Sodium

Calcium Fluoride Fluorine Calcium

List the products of the electrolysis of these molten salts.

Electrolysis of Lead Bromide

At the negaBve electrode (cathode)

PosiBve lead ions , Pb2+ , are acracted to the negaBve electrode. At the negaBve electrode, the ions collect electrons from the circuit. The lead ion turns back in to a lead atom.

At the posiBve electrode (anode)

•  At the posiBve electrode, bromide ions , Br-‐, lose electrons (to replace electrons taken by the lead).

•  The bromide ions combine to make bromine gas molecules.

Using ionic liquids à Electrolysis

Use the diagram to describe what happened with the demo of lead bromide.

ApplicaBon

Marking

What’s the link?

Electrolysis

Copper Sulphate soluBon CuSO4(aq)

PredicBon. What do you think is going to happen? ___________________________________________________________________________________________________________________________ ObservaBon. What do you see? Record your results ____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ Conclusion. Can you explain what you have seen? ____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

To predict the products of electrolysis 1. Find the correct ions your data sheet 2. IdenBfy which ion will go to which electrode (posiBve or negaBve) 3. Metal ions will form a molten metal, non-‐metals will usually form a gas and is normally 2 atoms in a molecule (e.g. F2 or Br2)

e.g. Lead Bromide 1.  Pb2+ Br-‐ 2.  Pb2+ goes to negaBve

electrode, Br-‐ goes to posiBve electrode

3.  Molten lead (Pb) is formed at negaBve electrode, Bromine gas (Br2) is formed at posiBve electrode

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All Name products

formed by electrolysis of molten solids

Describe the process of electrolysis of aluminium

Use half equaBons to show the reacBons at electrodes

Electrolysis

OILRIG -‐ OxidaBon and ReducBon

•  O oxidaBon •  I is •  L loss •  R reducBon •  I is •  G gain

•  When an atom loses electrons, this is called oxidaCon.

•  When an atom gains electrons, this is called reducCon.

Both processes happen in electrolysis.

Complete the table, you may choose where to begin:

FOUNDATION

HIGHER

Hint: Remember to balance the electrons How many Br-‐ ions in total are needed to make Br2? How many electrons in total are lost?

Extension: Where is oxidaBon happening? Where is reducBon happening? Use OILRIG to help

Complete the table, you may choose where to begin:

FOUNDATION

HIGHER

Ionic EquaBons

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A sodium ion (Na+) gains an electron Na+ + e-‐ à Na

Bromide ion loses an electron to become Br2 Br-‐ à Br2 + e-‐

Is this correct??

Ionic EquaBons

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Bromide ions lose electrons to become Br2

2Br-‐ à Br2 + 2e-‐

Each bromide ion loses 1 electron, in total 2 electrons are lost!

Cl-‐

Cl-‐

Cl-‐

Cl-‐ Na+ Na+

Na+ Na+

OILRIG

-‐  ions LOSING electrons to become atoms is called ‘OXIDATION’ (even though oxygen may not be involved)

+ ions GAINING electrons to become atoms is called ‘REDUCTION’

OxidaCon is loss, reducCon is gain

‘OILRIG’

Uses of Electrolysis

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All Name products


Describe the process of electrolysis of aluminium oxide


What’s the link?

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All Name products


Describe the process of electrolysis of aluminium oxide


Aluminium Oxide GeHng aluminium from aluminium oxide (ore)

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All State ions present

in soluBons of compounds

Describe how the products are different for soluBons

Use the rules to idenBfy products for different soluBons

Electrolysis of SoluBons

So far we have looked at electrolysis of a molten compound

What happens when we have soluCons? (i.e.

including water)

What happens when the ionic compounds are dissolved in water?

Here, water molecules break up into HYDROGEN IONS, H+ and HYDROXIDE IONS OH-‐

H2O è H+ + OH-‐

So, in an ionic soluBon (eg sodium chloride soluBon), there will be FOUR types of ion present:

TWO from the ionic compound and TWO from the water (H+ + OH-‐)

SODIUM CHLORIDE SOLUTION NaCl (aq)

Cl-‐

Na+

OH-‐ H+ Na+

Cl-‐ OH-‐ H+

H+

OH-‐ Cl-‐

Na+

IONIC SOLUTION

Cl-‐

Na+

OH-‐ H+ Na+

Cl-‐

OH-‐

H+

H+

OH-‐ Cl-‐ Na+

Which ions gain or lose electrons (“get discharged”) and which stay in soluBon?

IONIC SOLUTIONS: At the CATHODE

+

At CATHODE: 2H+ + 2e-‐ H2

sodium ION, missing 1 electron

Hydrogen ATOM, NEUTRAL Na+ H

Na+

Na+

H+

H+

H

H

H+ hydrogen ION, missing 1 electron

As HYDROGEN is LESS REACTIVE than SODIUM, it is discharged. The sodium ions stay in solu0on.

which ions?

+

Cl-‐

Cl-‐

Cl-‐

Cl-‐

Cl Cl

Cl Cl

chloride ION, extra 1 electron

Cl-‐ Cl chlorine ATOM, NEUTRAL

At ANODE: 2Cl-‐ 2e-‐ + Cl2

IONIC SOLUTIONS: At the CATHODE – halogen compounds

If the – ion is a HALOGEN (Cl, Br, I) it is discharged and chlorine (or Br or I) is given off and the OH -‐ ions stay in solu0on

O H

O H O H

O H

O H hydroxide ION, from water extra electron

which ions?

+

nitrate ION, extra 1 electron NO3

-‐ Oxygen atom

At CATHODE: 4OH-‐ 2H2O + O2 + 4e-‐

O H

H

IONIC SOLUTIONS: CATHODE – non halogen compounds

NO3-‐

NO3-‐

O H

hydroxide ION, OH-‐ from water, extra electron

O

NO3-‐

NO3-‐

O H

O H

O

If the – ion is NOT a halogen (eg nitrate, sulphate etc) then the HYDROXIDE ions from the water are discharged to make WATER and OXYGEN gas. The other ions stay in soluBon.

which ions?

+ ANODE Acracts – ions (‘Anions’)

If – ions are HALOGENS ie chloride Cl-‐

bromide Br-‐

iodide I-‐ the __________ is produced.

If – ions are NOT HALOGENS Eg sulphate SO4

2-‐, nitrate NO3-‐

carbonate CO32-‐

__________ is produced.

-‐ CATHODE Acracts + ions (‘CaBons’)

If + ions (metals) are _______________________

K, Na, Ca, Mg, Zn, Fe

Then __________ is produced

If + ions (metals) are LESS REACTIVE than hydrogen

Cu, Ag, Au

Then the _______ is produced

RULES FOR IONIC SOLUTIONS

+ ANODE Acracts – ions (‘Anions’)

If – ions are HALOGENS ie chloride Cl-‐

bromide Br-‐

iodide I-‐ the HALOGEN is produced.

If – ions are NOT HALOGENS Eg sulphate SO4

2-‐, nitrate NO3-‐

carbonate CO32-‐

OXYGEN is produced.

-‐ CATHODE Acracts + ions (‘CaBons’)

If + ions (metals) are MORE REACTIVE than hydrogen

K, Na, Ca, Mg, Zn, Fe

Then HYDROGEN is produced

If + ions (metals) are LESS REACTIVE than hydrogen

Cu, Ag, Au

Then the METAL is produced

RULES FOR IONIC SOLUTIONS

potassium chloride

Compound State Anode (+) Cathode (-) Ions

molten K+ Cl-‐ potassium chlorine

aluminium oxide molten

copper chloride soluCon

sodium bromide soluCon

silver nitrate soluCon

potassium chloride soluCon

zinc sulphate soluCon

(REACTIVITY: K+ Na+ Ca2+ Mg2+ Al3+ Zn2+ Fe3+ H+ Cu2+ Ag+ Au3+ )


potassium chloride

Compound State Anode (+) Cathode (-) Ions

molten K+ Cl-‐ potassium chlorine

aluminium oxide molten Al3+ O2-‐ aluminium oxygen

copper chloride soluCon Cu2+ Cl- H+ OH- copper chlorine

sodium bromide soluCon Na+ Br- H+ OH- hydrogen bromine

silver nitrate soluCon Ag+ NO3- H+ OH- silver oxygen

potassium chloride soluCon K+ Cl- H+ OH- hydrogen chlorine

zinc sulphate soluCon Zn+ SO42- H+ OH- hydrogen oxygen



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