Question

1) Using Pauling’s Rules, give the approximate pKa values for the following acids.

a. H3PO3 b. HNO3 c. HClO4 d. H5IO6

pKa1 = pKa2 =

pKa1 =
pKa1 =
pKa1 = pKa2 =

2) Select the best answer and give the basis for your selection.

a. Thermally most stable: PH4Cl, PH4Br, PH4I
b. Strongest acid: H2O, H2S, H2Se, H2Te
c. Acidic oxide: Ag2O, V2O5, CO, Ce2O3

d. Stronger base (toward a proton): PH2-, NH2-

3) Would the following increase, decrease, or have no effect on the acidity of the solution?

a. Addition of Li3N to liquid NH3
b. Addition of HgO to an aqueous KI solution
c. Addition of CH3CO2K to liquid NH3

d. Addition of KHSO4 to H2SO4
e. Addition of Al(OH)3 to aqueous NaOH

Answer 1

Answer of 1.

Pauling's rule for oxoacids, pKa of oxoacid is (O)_pE(OH)_q

pKa₁= 8-5p, succesive pKa values can be found by adding 5 per ionisation.So, pKa₂= pKa₁ +5, pKa₃=pKa₂ +5

A. Now for H₃PO_4,

first rewrite it as the form used O₁HP(OH)₂

so. pKa₁ = 8-51= 3, pKa₂= 3+5= 8

B. For, HNO₃ it can be rewritten as, (O)₂N(OH)

pKa = 8-52= -2

C. For HClO₄

It can be rewritten as

(O)₃Cl(OH)

pKa = 8-53= -7

D. For H₅IO₆

It can rewritten as OI(OH)₅

pKa₁ = 8-51= 3

pKa₂= 3+5=8