extraction of pure elements from nature

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Extraction of Pure Elements from Nature Which elements are easy?

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Extraction of Pure Elements from Nature. Which elements are easy?. Easy elements are gases that exist in the elemental form. N 2 , O 2 , noble gases Obtained by distillation of cooled, liquified air. Preview. Extraction of Metals. - PowerPoint PPT Presentation

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Page 1: Extraction of Pure Elements from Nature

Extraction of Pure Elements from Nature

Which elements are easy?

Page 2: Extraction of Pure Elements from Nature

Easy elements are gases that exist in the elemental form

N2, O2, noble gases

Obtained by distillation of cooled, liquified air.

Page 3: Extraction of Pure Elements from Nature

Preview

Page 4: Extraction of Pure Elements from Nature

Extraction of Metals

All metals exist as cations in chemical compounds in the crust. Key: reducing the cations to the neutral metal.

Example: Fe2O3 has Fe3+ ions. To obtain Fe metal, need to add 3 electrons to each Fe3+ ion.

Page 5: Extraction of Pure Elements from Nature

What we’ll find.

Page 6: Extraction of Pure Elements from Nature

Review of Thermodynamic Control of Reactions

is negative, then the reaction is favored

o o o

o

G H T S

If G

Enthalpy: H depends on bond strengthreactions favored by negative H (which is forming stronger bonds)

Entropy: S depends on randomness (disorder)reactions favored by positive S

(increasing disorder, particularly formation of gases)

Page 7: Extraction of Pure Elements from Nature

Consider the decomposition of Fe2O3

Decomposition Reaction: 2 Fe2O3(s) 4 Fe(s) + 3 O2(g)

Ho =

So =

Go =

Temperature where Go is negative?

Page 8: Extraction of Pure Elements from Nature

Consider the reaction of Fe2O3 with C

Reaction with C: 2 Fe2O3(s) + 3 C(s) 4 Fe(s) + 3 CO2(g)

C(s) 0 5.6

CO2(g) -393.5 213 -394.4

Ho =

So =

Go =

Temperature where Go is negative?

Page 9: Extraction of Pure Elements from Nature

Consider the decomposition of HgO

2 HgO(s) 2 Hg(l) + O2(g)

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Aluminum Production

2 Al2O3(dissolved) + C(s) 4 Al(l) + 3 CO2(g)

Page 13: Extraction of Pure Elements from Nature

Aluminum Production2 Al2O3(dissolved) + C(s) 4 Al(l) + 3 CO2(g)

Why use carbon instead of just a metal electrode?

Go 2 Al2O3(s) 4 Al(s) + 3 O2(g) = + 3164 kJ/mol

Eo =

Go 2 Al2O3(s) + 3 C(s) 4 Al(s) + 3 CO2(g) = + 1981 kJ/mol

Eo =

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Gold!4 Au(s) + 8 NaCN(aq) + O2(g) + 2 H2O(l) 4 NaAu(CN)2(aq) + 4 NaOH(aq)

Page 18: Extraction of Pure Elements from Nature

Photography Chemistry

Exposure: AgX Ag(s) + X(s)

Page 19: Extraction of Pure Elements from Nature

Photography Chemistry

Developing: AgX(s) + e- Ag(s) + X-(s) HQ Q + 2 H+ + 2e-

Page 20: Extraction of Pure Elements from Nature

Photography ChemistryFixing: AgX(s) + 2 Na2S2O3(aq) Na3[Ag(S2O3)2](aq) + X-(aq)

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Photography Chemistry