Zinc
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| Other names/abbreviations: | Zn |
| Element no: | 30 |
| Element group: | 12 (IUPAC) II B (American labelling) II B (European labelling) |
| Element type: | Metals |
| CAS-Number: | 7440-66-6 |
| EINECS-Number: | 231-175-3 |
Chemical properties
Reaction of zinc with acidsZinc metal dissolves slowly in dilute sulphuric acid to form Zn(II) ions and hydrogen, H2. In aqueous solution the Zn(II) ion is present as the complex ion [Zn(H2O)6]2+.
Zn (s) + H2SO4 (aq)
Zn2+ (aq) + SO42- (aq) + H2 (g)When using an oxidizing acid like HNO3 the anion is reduced:
4 Zn (s) + NO3- (aq) + 10 H+ (aq)
4 Zn2+ (aq) + NH4+ (aq) + H2O (l)Reaction of zinc with air
Zinc reacts with oxygen in moist air. The metal burns in air to form zinc(II) oxide, a material that goes from white to yellow on prolonged heating.
2 Zn (s) + O2 (g)
2 ZnO (s) [white]Reaction of zinc with ammonia
Zn(II) is precipitated by ammonia ions as Zn(OH)2 (white amorphous precipitate)
Zn2+ (aq) + 2 NH3 (aq) + 2 H2O (l)
Zn(OH)2 (s) + 2 NH4+ (aq)By excess ammonia, the precipitate is dissolved [1]
Zn(OH)2 (s) + 4 NH3 (aq)
[Zn(NH3)4]2+ (aq) + 2 OH- (aq)Reaction of zinc with halogens
Zinc will react with gaseous bromine, Br2, and iodine, I2.
Zn (s) + Br2 (g)
ZnBr2 (s) [white]Zn (s) + I2 (g)
ZnI2 (s) [white]Reaction of zinc with hexacyanoferrate
Zn (II) is precipitated by potassium hexacyanoferrate ions as K2Zn[Fe(CN)6] (white precipitate)
Reaction of zinc with hydroxide ions
Elemental zinc reacts with strong bases forming hydrogen:
Zn (s) + 2 OH- (aq)
Zn(OH)2 (s) + H2(g)Zn2+ is precipitated by hydroxide ions as Zn(OH)2 (white amorphous precipitate) [1]
Zn2+ (aq) + 2 OH- (aq)
Zn(OH)2 (s)By acid excess hydroxide, the precipitate is dissolved [1]
Zn(OH)2 (s) + 2 H+ (aq)
Zn2+ (aq) + 2 H2O (l)Zn(OH)2 (s) + 2 OH- (aq)
[Zn(OH)4]2- (aq)Reaction of zinc with sulfide
Zn (II) is not precipitated by sulfide ions at 0.4 M HCl, but at all pH ≥ 3:
Zn2+ (aq) + HS- (aq) + OH- (aq)
ZnS (s)[Zn(OH)4]2- (aq) + HS- (aq) + 2 H+ (aq)
ZnS(s) + 3 H2O (l) + OH- (aq)Reaction of zinc with water
Elemental zinc will reduce steam at high temperatures [1]:
Zn (s) + H2O (g)
ZnO (s) + H2 (g) , ΔH = -106.4 KJSolubility
Water: 10 mg/m3 (Reaction, 20°C) [5]
Quantitative analysis
Method 3500-Zn C Inductively Coupled Plasma Method [2]. 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 = 0.01 mg/L
Method limit of detection in soil = 1.00 mg/kg
Safety
Symbol: -R-phrases: 10-15
S-phrases: 7/8-43
Physical properties
Appearance | ||
| Physical state @ 20°C: | Solid [5] | |
| Color: | Gray [5] | |
| Odor: | Odourless [5] | |
Bulk properties | ||
| Molecular weight (g/mol): | 65.39 [3] | |
| Melting point (°C): | 419.5 [3] | |
| Boiling point (°C): | 907 [3] | |
| Density (g/cm3): | 7.14 [3] | |
| Molar volume (cm3): | 9.16 (20°C) [4] | |
| Velocity of sound (m/s): | 3700 | |
| Elastic properties: Young's modulus (GPa): Rigidity modulus (GPa): Bulk modulus (GPa): Poisson ratio: |
94-105 [4] 37-42 [4] 69 [4] 0.25-0.35 [4] | |
| Hardness: Mineral hardness: Brinell hardness (MN/m2): |
2.5 412 | |
Thermodynamic properties | ||
| ΔH°atomization (KJ/mol): | 129.3±2.9 [3] | |
| ΔH°fusion (KJ/mol): | 7.28±0.01 [3] | |
| ΔH°vaporization (KJ/mol): | 114.2±1.7 [3] | |
| Cp (solid) (J/K·mol): | 25.3163 (20 °C) [4] 26.1647 (100 °C) [4] 26.9311 (200 °C) [4] 28.0532 (300 °C) [4] 28.9016 (400 °C) [4] | |
| Coeff. of linear thermal expansion (106 K-1): | 31 (20 °C) [4] 31 (100 °C) [4] 33 (200 °C) [4] 34 (300 °C) [4] | |
Crystal structure | ||
| Crystal type | HCP [4] Hexagonal | |
Electronic properties | ||
 |
Electron configuration: | 1s2-2s2-2p6-3s2-3p6-3d10-4s2 |
| Atomic radius (Å) | 1.53 | |
| Ionic radius (Å): | Zn(II): 0.74 [3] | |
Conductivity | ||
| e°(V): | Zn(II)/Zn: -0.7619 [3] | |
| Electrical resisitvity (μΩ·cm): | 5.96 (20 °C) [4] 7.80 (100 °C) [4] 11.0 (200 °C) [4] 13.0 (300 °C) [4] 16.5 (400 °C) [4] | |
| Thermal (W/m·K): | 113 (20 °C) [4] 109 (100 °C) [4] 105 (200 °C) [4] 101 (300 °C) [4] 96 (400 °C) [4] | |
References
1: General chemistry7th edition (1984) Edited by Holtzclaw, Jr.,H.F., Robinson,W.R. & Nebergall,W.H. pp. 1-932. D.C. Heath and Company. Lexington
2: Standard Methods for the Analysis of Water and Wastewater, APHA, 1992, 18th edition
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: Merck. ChemDAT The Merck Chemical Database Ver. 1.1.5
© Michael Pilgaard
Created: April 29, 2006
Last update: October 31, 2008