Suppose a chloride ion and a sodium ion are separated by a center—center distance of 5 Å. Is
the interaction energy (the energy required to pull them infinitely far apart) predicted to be larger if the medium between them is water, or if it is n-pentane? (See Table 2.5)
If Ca2+, Na+ and F¯ each have ionic radii ~1.16. Which ionic bond is stronger: Ca-F or Na-F? If Ca2+ is often bound on the surface of a protein by carboxylic acid functional groups. If the pKa of a particular -COOH group is 4.2, would you predict Ca2+ to be most tightly bound at pH 8, pH 4.2, or pH 3? Explain your answer.
Table 2.5 Important properties of liquid water compared with those of n-pentane, a nonpolar,
Nonhydrogen-bonding liquida
Interpretation:
Interaction energy will be more in which of the given ion pairs must be predicted. The stronger ionic bond must be predicted among the given ionic compounds. In which of the given pH the interaction between
Concept introduction:
Ionic interaction depends on Columbic interaction which depends on the charge of ions and distance by which those ions are separated. It aslo depends on the dielectric constant of the medium and the viscosity of the medium. The ionic bond is stronger when the size of the ions is small, charge in ions is high. Lattice energy depends on Columbic interaction. The bond between
The interaction energy between sodium ion and chlorine ion will be larger in case of n-pentane.
The interaction of ion pair will be more in case of n-pentane.
This is because the dielectric constant of n-pentane is
Now,
This is because of Columbic interaction
where
As calcium ion has the double charge of sodium ion so
The
This is because at pH greater than
So, the best pH is