Ionic compound reactions, physical properties of ionic compounds and geometry of CO2, CS2 and SO2

Question: Why ionic compounds reactions are rapid and covalent compounds reactions are much slower.

Answer. Ionic compounds exist in form of ions in aqueous solution and their reactions are rapid. This is because on mixing the solutions, no bond has to be broken, only a new bond is to form.

For example addition of silver nitrate solution and sodium chloride solution produce a white precipitate of silver chloride instantaneously. On the other hand, reactions of covalent compounds are much slower as they involve bond breaking and bond formation.

Question: Explain why are the melting points, boiling points, heat of vaporization and heat of sublimations of electrovalent compounds higher as compared with those of covalent compounds.

Answer. In the electrovalent compounds(ionic compound) ions are held together by strong electrostatic force of attraction. So they have high melting points, boiling points, heat of vaporizations and heat of sublimation. On the other hand, covalent compounds are held together by relatively weak van der Waal forces. So such compounds have very low melting point, boiling points, heat of vaporizations and heat of sublimation.

Question: Why are the dipole moments of CO2 and CS2 zero, but that of SO2 is 1.61D.

Answer. Dipole moment of CO2 and CS2 are zero because CO2 and CS2 have a linear structure, where the dipoles are equal and opposite, cancel each other effect. Whereas dipole moment of SO2 shows that SO2 has not the linear structure. A linear SO2 molecule could have zero dipole moment. Calculations show that CS2 has a bent or angular structure with dipole moment of 1.61 D. μ = 0 D μ = 0 D μ = 1.61 D.

Question: The abnormality of bond length and bond strength in HI is less prominent than HCl, why? Answer. This abnormality in bond length and strength is due to ionic character present in the molecule. More the ionic character, greater will be abnormality and vice versa. As HCl has greater ionic character due to relatively greater electronegativity of Cl . So it has shorter bond length and stronger bond strength than HI which lower ionic character due to lower electronegativity of I .

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