Entrance Exams
Govt. Exams
The orange color arises from charge transfer between oxygen and chromium, not from d-d transition within Cr³⁺.
Excess oxygen converts P₄ to P₄O₁₀ (phosphorus pentoxide). Limited oxygen gives P₄O₆.
+3 is the most stable oxidation state for Cr with d³ configuration. Cr³⁺ complexes are highly stable.
Be and Al show diagonal relationship due to similar charge-to-radius ratio. Both form covalent compounds and amphoteric oxides.
Borax solution is basic because borate ions undergo hydrolysis: BO₃³⁻ + H₂O ⇌ HBO₃²⁻ + OH⁻, producing OH⁻ ions and making the solution basic.
SiO₂ acts as a flux. It combines with Fe₂O₃ (formed from iron oxidation) to form iron silicate slag (FeSiO₃), which is removed from molten copper.
Reducing power increases with increasing size of halogen (decreasing electronegativity). HI is the strongest reducing agent due to the weak H-I bond.
Transition metals from 3d, 4d, and 5d series can form stable carbonyl complexes. Examples include Fe(CO)₅, Ni(CO)₄, Mo(CO)₆, and W(CO)₆.
Thermal stability of hydrides decreases down the group due to decreasing bond strength (H-O > H-S > H-Se > H-Te). The H-O bond is the strongest.
In this reaction, HCl acts as a reducing agent because Cl⁻ (oxidation state -1) is oxidized to Cl₂ (oxidation state 0). Mn in KMnO₄ is reduced from +7 to +2.