Aluminum
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| Other names/abbreviations: | Al |
| Element no: | 13 |
| Element group: | 13 (IUPAC) III B (American labelling) III B (European labelling) |
| Element type: | Metals |
| CAS-Number: | 7429-90-5 |
| EINECS-Number: | 231-072-3 |
Chemical properties
Reaction of aluminium with acidsAluminium dissolves readily in dilute sulphuric or hydrochloric acid under the formation of Al(III) and hydrogen H2. Concentrated nitric acid passivates aluminium metal.
2 Al (s) + 3 H2SO4 (aq)
2 Al3+ (aq) + 2 SO42- (aq) + 3 H2 (g)2 Al (s) + 6 HCl (aq)
2 Al3+ (aq) + 6 Cl- (aq) + 3 H2 (g) [2]Reaction of aluminium with air
Aluminium reacts with oxygen, forming a protective layer of alumnium(III) oxide that prevents further reaction with oxygen. Like magnesium, aluminium burns in oxygen with a brilliant white flame. The product in this reaction is also alumnium(III) oxide.
4 Al (s) + 3 O2 (g)
2 Al2O3 (s)Reaction of aluminium with ammonia
Aluminum ions are precipitated by NH3 as Al(OH)3. Al does not form complexes with NH3. NH4+ precipitates the [Al(OH)3]- complex upon evaporation of NH3.
[Al(OH)4]- (aq) + NH4+ (aq)
Al(OH)3 (s) + NH3 (g) + H2O (l)Reaction of aluminium with carbonates
Aluminum ions are precipitated by carbonate as Al(OH)3 due to the equilibrium:
CO32- (aq) + H2O (l)
HCO3- (aq) + OH- (aq)[Al(H2O)6]3+ (aq) + 3 OH- (aq)
[Al(OH)3(H2O)3] (s) [white] + 3 H2O (l)The hydroxide is partially soluble in excess alkalimetal carbonate.
[Al(OH)3(H2O)3] (s) + 3 OH- (aq)
[Al(OH)6]3- (aq) + 3 H2O (l)Reaction of aluminium with halogens
Aluminium metal reacts vigorously with all the halogens to form aluminium(III) halides.
2 Al (s) + 3 Cl2 (g)
2 AlCl3 (s)2 Al (s) + 3 Br2 (g)
Al2Br6 (s)2 Al (s) + 3 I2 (g)
Al2I6 (s)Reaction of aluminium with hydroxide ions
Aluminium dissolves in sodium hydroxide with the formation of hydrogen gas, H2, and the formation of aluminates of the type [Al(OH)4]-.
2 Al (s) + 2 NaOH (aq) + 6 H2O (l)
2 Na+ (aq) + 2[Al(OH)4]- (aq) + 3 H2 (g) [2]Aluminum ions are precipitated by OH- as a white gelatinous precipitate [2]:
Al3+ (aq) + 3 OH- (aq)
Al(OH)3 (s) Ksp = 1.9·10-33At excess OH- the Al(OH)3 is dissolved:
Al(OH)3 (s) + OH- (aq)
[Al(OH)4]- (aq)Reaction of aluminium with phosphates
Aluminum ions are precipitated by hydrogen phosphate ions as AlPO4 in neutral and acetic solutions (white precipitate):
Al3+ (aq) + H2PO4- (aq)
AlPO4 (s) + 2H+ (aq)The precipitate is readily soluble in strong acids and bases:
AlPO4 (s) + 3 H+ (aq)
Al3+ (aq) + H3PO4 (aq)AlPO4 (s) + 4 OH- (aq)
[Al(OH)4]- (aq) + PO43- (aq)Reaction of aluminium with sulfide
Aluminum is not precipitated by sulfide ions at 0.4M HCl. Sodium sulfide will precipitate Al-ions as Al(OH)3 [2]:
S2- (aq) + H2O (l)
HS- (aq) + OH- (aq)Al3+ (aq) + 3 OH- (aq)
Al(OH)3 (s)Misc. reactions of aluminium
Thermite reaction [2]:
2 Al (s) + Fe2O3 (s)
2 Fe (s) + Al2O3 (s) ΔH° = -851.4 KJ
Solubility
Water: Insoluble (20 °C) [6]
Quantitative analysis
Method 3500-Al C Inductively Coupled Plasma Method [1]. A portion of the sample is digested in a combination of acids. The digest is aspirated into an 8,000 K argon plasma where resulting light emission is quantified for 30 elements simultaneously.Method limit of detection in water = 0.05 mg/L
Method limit of detection in soil = 100 mg/kg
Safety
Symbol: FR-phrases: 15-17
S-phrases: 7/8-43
Physical properties
Appearance | ||
| Physical state @ 20°C: | Solid [6] | |
| Color: | Silvery [6] | |
| Luster: | Metallic - Dull | |
| Transparancy: | Opaque | |
| Odor: | Odourless [6] | |
Bulk properties | ||
| Molecular weight (g/mol): | 26.981538(2) [3] | |
| Melting point (°C): | 660.45 [3] | |
| Boiling point (°C): | 2520 [3] | |
| Ignition temp. (°C): | 400 (Approximately) [6] | |
| Density (g/cm3): | 2.699 [3] | |
| Molar volume (cm3): | 12.07 (20 °C) [4] | |
| Velocity of sound (m/s): | 5100 | |
| Elastic properties: Young's modulus (GPa): Rigidity modulus (GPa): Bulk modulus (GPa): Poisson ratio: |
62-72 [4] 25-26 [4] 75 [4] 0.32-0.36 [4] | |
| Hardness: Mineral hardness: Brinell hardness (MN/m2): Vicker hardness (MN/m2): |
2.75 [3] 245 167 | |
Optical properties | ||
| Reflectivity (%): | 71 | |
Thermodynamic properties | ||
| ΔH°atomization (kJ/mol): | 326 | |
| ΔfH°gas (kJ/mol): | 329.7 (Monoatomic) [3] | |
| ΔH°fusion (kJ/mol): | 10.71 [3] | |
| ΔH°vaporization (kJ/mol): | 294 [3] | |
| S°gas (J/K·mol): | 164.6 [5] | |
| S°solid (J/K·mol): | 28.3 [5] | |
| ΔfG°gas (kJ/mol): | 289.4 [5] | |
| ΔfG°solid (kJ/mol): | 0 [2] | |
| Cp (solid) (J/K·mol): | 24.167 (20 °C) [4] 25.184 (100 °C) [4] 26.426 (200 °C) [4] 27.781 (300 °C) [4] 29.023 (400 °C) [4] | |
| Coeff. of linear thermal expansion (106 K-1): | 22.5 (20 °C) [4] 23.9 (100 °C) [4] 24.3 (200 °C) [4] 25.3 (300 °C) [4] 26.5 (400 °C) [4] | |
Crystal structure | ||
| Crystal type | Face centered cubic [4]. Isometric - Hexoctahedral H-M Symbol (4/m -3 2/m) Space Group: Fm3m,Pm3m. | |
| Lattice constant (Å): | 4.05 | |
| Cell dimensions: | a = 4.04, Den(Calc)= 2.72 | |
| Volume (Å3): | 65.94 | |
| Formula units per unit cell: | 4 | |
Electronic properties | ||
 |
Electron configuration: | 1s2-2s2-2p6-3s2-3p1 |
| Atomic radius (Å) | 1.82 | |
| Ionic radius (Å): | Al(III): 0.535 [3] | |
Conductivity | ||
| e°(V): | Al(III)/Al: -1.676 [3] Al(I)/Al: 0.55 [3] | |
| Electrical resisitvity (μΩ·cm): | 2.60 (20 °C) [4] 2.61 (25 °C) [4] 3.55 (100 °C) [4] 4.78 (200 °C) [4] 5.99 (300 °C) [4] 7.30 (400 °C) [4] | |
| Superconduction temp. (K): | 1.175 | |
| Thermal (W/m·K): | 221.5 (20 °C) [4] 203.0 (247 °C) [4] 284.5 (647 °C) [4] | |
| Electrical (Ω·m): | 17.08 (20 °C) [1] | |
References
1: Standard Methods for the Analysis of Water and Wastewater, APHA, 1992, 18th edition2: General chemistry
7th edition (1984) Edited by Holtzclaw, Jr.,H.F., Robinson,W.R. & Nebergall,W.H. pp. 1-932. D.C. Heath and Company. Lexington
3: Greenwood,N.N., Earnshaw,A. Chemistry of the elements
2nd edition (1997) Edited by Greenwood,N.N., Earnshaw,A. pp. 1-1340, Butterworth-Heinemann. Oxford. Great Britain
4: Buch,A. Pure Metals Properties. A Scientific-Technical Handbook
1st edition (1999) Edited by Buch,A. pp. 1-306, ASM International and Freund Publishing House Ltd. Ohio. USA
5: CRC Handbook of Chemistry and Physics
75th edition (1994) Edited by Lide,D.R. , CRC Press Inc. Boca Raton, USA
6: Merck. ChemDAT The Merck Chemical Database Ver. 1.1.5
© Michael Pilgaard
Created: April 29, 2006
Last update: May 5, 2008