1. Compare the ionic radii in Table 12.3 with the atomic radii in the inside cov

Question

1. Compare the ionic radii in Table 12.3 with the atomic radii in the inside cover of the book. Why are some ions larger and others smaller than the corresponding atoms? 2. The polymer nylon 6,6 consists of repeating units which have the chemical formula C12H22N202. What is the weight % of carbon in nylon? 3. For the Na+ - Cl pair the attractive and repulsive energies in eV per pair are given by E, =-1.436 Ea = 7.32 × 10-6 r- where r is the inter-ionic distance in nanometers (nm). The net energy Ev is the sum of the attractive and repulsive energies. On a single graph show the variation of ER, EA, and Ey as a function ofr in the range of 0.01 to 1 nm. a. b. Determine the inter-ionic distance ro and the bonding energy Eo of the Na+ -Clpair. c. Compare ro with the sum of the radii of the two ions (use Table 12.3)

Explanation / Answer

1 ) radius order : anion > neutral atom > cation

anions radius more than corresponding atoms . it is due to in anion there are more number of electrons than protons so less number of protons cannot hold good more protons so radius of anion is more.

size : I- > I ,   Cl- > Cl ,   Br- > Br

and cation radius is smaller than neutral atom it is due to in cation there are less number of electrons than protons . so more protons attaract strongly less number of electrons. so cation is smaller.

Mn+2 < Mn ,   Na+ < Na   ,   Mg+2   < Mg

2 ) C12H22N2O2 molar mass = 226 g/mol

in this molecule moles of carbon = 12

mass of C = 12 g/mol

mass of total C in nylon = 12 x 12 = 144 g/mol

% C = (144 / 226) x 100 = 63.7%

weight % of C = 63.7 %

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