Gases are made up of independent particles (atoms or molecules) moving in rapid motion in a straight line . The molecules/ atoms exert no attractive or repulsive forces between them .i.e they are independent. When the atoms collide with others or with any surface, there is no loss of velocity ( momentum is conserved) ,Continue reading “Assumptions of the kinetic molecular theory of ideal gas .”
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States of matter
Matter exists in three states (phases) ; Solid , Liquid and gaseous state . The three states of matter are interconvertible, as in same substance but in different state . E.g ice ( water in solid state) , liquid water and steam/ water vapour ( water in gaseous state ) . In the solid state,Continue reading “States of matter”
Five stages involved in metallurgy.
Mining ore from the ground. Separating and concentrating of the metal or the metal containing compound for further treatment. Reducing the ore to the free metal Refining or purifying the metal , increasing purity or improving the physical properties of the metal . Mixing with other elements to obtain the desired properties (alloys ) .
The permanganate ion MnO-⁴ is deep purple but TcO4- and ReO4- are colourless, explain.
The two oxides of Tc2O7 and Re2O7 are formed when metals are heated in air or oxygen. Both are yellow solids. Tc2O7 is more oxidizing than Re2O7 . Both oxides are soluble in water and form HTcO4 and HReO4 which are colourless. They contain TcO4- and ReO4- ions which are tetrahedral. TcO4- and ReO4- areContinue reading “The permanganate ion MnO-⁴ is deep purple but TcO4- and ReO4- are colourless, explain.”
The highest oxide of Fe is Fe2O3 while that of Ru is RuO4 . Explain
Ruthenium and Osmium form RuO4 and OsO4 which are in (+8) oxidation state. Ru(iii) and Os (+iv) are the most stable State. Ru(+v) , Os(vi) and Os ( viii) are also stable. Thus , a trend is observed that , on descending a group, the higher oxidation state become more stable . Therefore RuO4 andContinue reading “The highest oxide of Fe is Fe2O3 while that of Ru is RuO4 . Explain”
Metallic character of transition metals .
1) Electrical and thermal conductivity These elements are good conductors due to availability of mobile / free / delocalized electrons involved in metallic bonding. 2) Hardness They are generally hard ( cannot be cut with a knife) and brittle. Hardness is due to strong metallic bond between the atoms . The greater the number ofContinue reading “Metallic character of transition metals .”
Stability of complexes formed by transition elements .
1) Stability decreases with increase in atomic number of the elements. 2) For a given ligand , the complex containing the metal in higher oxidation state is the more stable one . E.g [Co(NH3)6]³+ is more stable than [Co(NH3)6]²+ . This is due to the fact that the higher the oxidation state, the metal cationContinue reading “Stability of complexes formed by transition elements .”
Briefly explain why the Zinc and scandium are not classified among the transition elements.
✓ Both have no ion that has a partially filled d-orbital . Zinc Forms only one ion ( other transition elements forms two or more ) Zn²+ has a completely full 3d sub-shell . Zn²+ has the following electronic configuration 1s²2s²3s²3p⁶3d¹⁰ or [Ar] 3d¹⁰ . Scandium Forms only one ion . Sc³+ has no 3dContinue reading “Briefly explain why the Zinc and scandium are not classified among the transition elements.”
Why is vanadium v oxide such a versatile catalyst.
Vanadium is a transition element . Most transition elements and their compounds suit to be industrial and biological catalysts due to the following reasons; Due to their ability to show variable oxidation states . Form complexes , a complex is a central metal ion /atom surrounded by ligands that are coordinately bounded to the CentralContinue reading “Why is vanadium v oxide such a versatile catalyst.”
In the extraction of tungsten metal, WO3 is reduced with hydrogen gas . Why is it not advisable to use carbon for the reduction?
Tungsten is found in the form of tungstate , the chief ores being Wolframite (FeWO4 and MnPO4) , schelite( CaWO4) and stolzite ( PbWO4) . The small amounts of MoS2 in the ores are concentrated by the foam floatation process . This is converted to WO3 . It is reduced to metal with hydrogen, reductionContinue reading “In the extraction of tungsten metal, WO3 is reduced with hydrogen gas . Why is it not advisable to use carbon for the reduction?”
Explain why TiO2 ( Titanium dioxide) is preferred to basic lead carbonate { 2PbCO3.Pb(OH)2} as a white paint pigment?
Titanium dioxide is mainly used as a white pigment base in paints . Pigment grade titanium dioxide may be prepared by either sulphate or chloride process because the naturally occurring rutile is colored by impurities like iron e.t.c . In this case, it has replaced {PbCO3.Pb(OH)2} due to the fact that; White lead forms PbSContinue reading “Explain why TiO2 ( Titanium dioxide) is preferred to basic lead carbonate { 2PbCO3.Pb(OH)2} as a white paint pigment?”
Why enthalpies of atomisation of transition elements are high .
This is due to effective nuclear charge and large number of valence electrons. This results to formation of strong metallic bond in metals . Effective nuclear charge (Z+) is the net positive charge experienced by an electron in a multi-electron atom .
Electron affinity across a period.
Electron affinity increases across a period in a similar manner as ionization energy. However, the electron affinity values are smaller than those in ionization energy since the electron removal from negative ions is easier than removal from neutral ions
Shielding
This is the balance between the pull of protons on the valence electrons and repulsion forces from inner electrons. Transition metals have low shielding effect. Transition metals easily lose electrons or ionized easily.
Ionization energy
Ionization energy is the minimum amount of energy needed to completely remove the valence electrons from the atom/ion and is directly related to the force of attraction on the electrons . The larger the nuclear charge and smaller radii of atom the larger the ionization energy (IE) . Ionization energy is also more for halfContinue reading “Ionization energy”
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