Entrance Exams
Govt. Exams
Diamond = 10 on Mohs scale.
Evaporation = liquid to gas.
Carbon atomic number = 6.
Lattice enthalpy depends inversely on ionic radius and directly on ionic charge.
CsI has the lowest lattice enthalpy (~604 kJ/mol) because both Cs⁺ and I⁻ are large ions with 1+ and 1- charges respectively.
In contrast, MgO has very high lattice enthalpy due to small, highly charged ions (Mg²⁺ and O²⁻), while NaCl and CaF₂ have intermediate values.
In the carbonate ion CO₃²⁻, the central carbon atom forms three sigma bonds with oxygen atoms and is involved in resonance structures with delocalized pi electrons.
This trigonal planar geometry requires sp² hybridization, with three hybrid orbitals arranged at 120° angles and one unhybridized p orbital for pi bonding.
Potassium hexacyanoferrate(III) contains both ionic bonds (between K⁺ and the [Fe(CN)₆]³⁻ complex) and covalent bonds (between Fe and CN ligands, and within the CN groups).
This complex salt is extensively used in coordination chemistry and analytical procedures like the Prussian blue test.
The balanced equation for this redox reaction in acidic medium is: 2KMnO₄ + 5H₂C₂O₄ + 3H₂SO₄ → K₂SO₄ + 2MnSO₄ + 10CO₂ + 8H₂O.
Potassium permanganate acts as an oxidizing agent (Mn⁷⁺ → Mn²⁺), while oxalic acid is oxidized (C²⁺ → C⁴⁺), giving the 2:5 molar ratio.
Fluorine has the highest electronegativity value of 3.98 on the Pauling scale, making it the most electronegative element.
This is because it has the smallest atomic radius and the highest effective nuclear charge among all elements, causing it to attract electrons most strongly in a chemical bond.