Inorganic Chemistry Practical Report

INORGANIC CHEMISTRY PRACTICAL REPORT November 6th 2008 Transition Element Student would do practical to observation characteristic of transition elements, like the color of the elements. Transition elements generally can make a complex compound. The practical has several aims as follows: • The aims of the 1st trial is student can observation about characteristic of transition elements in the compound • The aims of the 2nd trial is student can make complex compound and student can do classification what kind of complex compound that they have make. Principle of the practice: • Transition elements in a compound have color characteristic. This elements have 2 oxidation number or more, because the energy of electron in 3d orbital is almost similar, this is mean to get stability, the elements should to free an electron in the different sum to make an ion. • The positif metal ion (kation) and a sum of coordination pattern (ligan) make complex compound, generally is kation from transition elements. Reaction: • Cu(OH)2.CuSO4↓ + 8 NH3 → 2[Cu(NH3) 4]2++SO42• Co(OH)NO3 +6 NH3→ [Co(NH3) 6]2+ + NO3- + OH • Ni(OH)2↓ + 6NH3 → [Ni(NH3) 6]2+ + 2 OH• Zn(OH)2 ↓ + 4 NH3 ⇔ [Zn(NH3) 4]2+ + 2 OH• Cr(OH)3 ↓ + 6 NH3 → [Cr(NH3) 6]3+ + 3 OH-

Tools and materials: o test tube o dropping pipette o solution of cobalt , nickel, zink and chromium o chemistry compound materials like potassium dichromate, potassium chromate, potassium permanganate, mangan dioxide, sulfuric ferrat, dinitroso cobalt, dichloro nickel. Method: 1. color identification o identify the color of transition elements o find the oxidation number o write the result 2.

make a complex compound o put Cu2+ solution into a test tube, add an ammonia solution until formed a sediment o add an ammonia till over o observation what will happen next observation compound K2Cr2O7 K2CrO4 KmnO4 MnO2 FeCl3 FeSO4 Co(NO3)2 NiCl2

Oxidation number +6 +6 +7 +4 +3 +2 +2 +2

color Orange Yellow Light black Black Yellow gold green

Treatment Ni2+ + NH4OH, +>>> (Transparent light green) Cu2+ + NH4OH, +>>> (transparent light blue) Co2+ + NH4OH, +>>> (transparent light red) Zn2+ + NH4OH, +>>> (no color) Cr3+ + NH4OH, +>>> (bluish black)

Observation Light blue, light blue solution Dark blue, dark blue solution Blue greenish, no color solution White sediment, no color solution Green grayish , gray solution

Discussion Transition elements or metal elements position between an elements of earth alkaline. Transition elements stay in block d orbital on the periodic system. Characteristic from the elements is have more than a kind oxidation number (except Sc and Zn). Electron energy in 3d orbital are almost similar. This is mean to get stability, the elements make an ion with free an electron in the different sum. Because of that, this elements have two or more oxidation number in compound. The other character from transition elements in generally is stay in d or f orbital which is not full yet. So the atomic, free elements and the compound can have not in pair electron. This is support the paramagnetic characteristic of transition. A lot of transition compound have a specific color. Transition elements can shape a complex compound. Every ion of transition metal make a complex which is have specific color. Ion with a different oxidation grade have a different color. Coordination compound create from positif metal ion, called central atomic. And amount of coordination pattern called ligan. Positif ion as lewis acid and ligan as lewis base. Generally, kation which is can make coordination compound is ion of transition elements. Ligan is a must to have minimum a pair of free electron in the orbital bond. Comparison of ligan and central atomic is the important factor to decide how much the capacity to get a maximum ligan. Conclusion in general, transition elements have a variant oxidation number. i. Compound character is paramagnetic ii. Transition elements can make complex compound iii. Complex compound have specific color

References

Ahmad,hiskia.2001.kimia unsur dan radiokimia.Bandung:PT.Citra aditya bakti. Keenan,charles.w.1992.kimia untuk universitas edisi keenam kedua.Jakarta:Erlangga.

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