&ionic&liquids& - co-op academy failsworth - · pdf file ·...
TRANSCRIPT
06/05/15
Ionic Liquids
Some
Most
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
Some
Most
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
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
Most
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
Ionic Liquids
Some
Most
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
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?
Some
Most
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 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.
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.
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.
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
Some
Most
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
Ionic EquaBons
Some
Most
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
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
Some
Most
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
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
Some
Most
All Name products
formed by electrolysis of molten solids
Describe the process of electrolysis of aluminium oxide
Use half equaBons to show the reacBons at electrodes
Some
Most
All Name products
formed by electrolysis of molten solids
Describe the process of electrolysis of aluminium oxide
Use half equaBons to show the reacBons at electrodes
Aluminium Oxide GeHng aluminium from aluminium oxide (ore)
Some
Most
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+ )
(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
(REACTIVITY: K+ Na+ Ca2+ Mg2+ Al3+ Zn2+ Fe3+ H+ Cu2+ Ag+ Au3+ )
(REACTIVITY: K+ Na+ Ca2+ Mg2+ Al3+ Zn2+ Fe3+ H+ Cu2+ Ag+ Au3+ )