Question

(7) Use HSAB theory to predict the following reactions will go or not go (a) CH3-CH3 + H2O → CH,OH+CH (AH = 12 kcal/mol) (b) CH3COCH3 + H2O → CH3COOH + CH, (AH--13 kcal/mol ) (6%) (8) Predict the order of solubility: (9%) (a) MgSO4, CaSO4, SISOs, and Baso. (c) AgF, AgCl, AgBr, and Ag! (b) PbCI, PbBry, and Pbi! (9) List the following acids in order of acid strength in aqueous solution: Using pKa (9-7n) to predict the order. (6%) (a) HMnO4 H:AsO H,SO; H2SO4 (b) HCIO HCIO HCIO: HCIO (10) Use the absolute hardness to arrange the hardness order for the following ? (a) H,O, NH, and PH; (b) OH, NH3, and NO, (e ) what is the 7 value for the hardest one among the 6 compounds ? (9%) I AXA H0 12.6 -6.4 1 3. 9 3. 13 NH, 10.7 -5.6 2.6 PH, 10.0 -1.9 4.1 OH 13.17 1.83 7.50 NO, 10.1 2.3 6.2 (11) (a) Which is the strongest Brønsted acid: SnHg, SbH, Tel (b) Which is the strongest Brønsted base: NH, PH, SbH; (c) Which is the strongest base to react with H":NH, CH,NH2, (CH)2NH. (CH),N (9%) (12) Use HSAB theory to predict the following reactions? (15 %) (a) OHors is more likely to form insoluble salts with M TM ions Will Cu?* react more strongly with (b) OH or NH,? (c) 0 2 or S?? Will Ag" react more strongly with (d) NH, or PH,? (e) Which one will react more strongly with CO: Fe, Fe 2 or Fe?

question 7 8 9 10 11 12

Answer 1

According to HSAB Principal, the term “hard”applies to those species which are smaller in size due to which they are hard to be polarized, while term “soft” applies to those species which are larger in size and are easily polarisable. The principle is simple, “hard go with hard and soft goes with soft”.

Higher oxidation states means they are hard, while lower means easily polarisable i.e soft.

Q7 (a) In this reaction CH₃CH₃ + H₂O è CH₃OH + CH₄, this reaction is impossible

(b) CH3COCH3 + H2O è CH3COOH + CH4, THIS REACTION IS IMPOSSIBLE

Q8 a) decreasing order of solubility: MgSO₄ > CaSO₄ > SrSO₄ > BaSO₄

                       b) PbBr₂ > PbCl₂ > PbI₂

                       C) AgF > AgBr> AgCl > AgI

Q9 (a) increasing acidic strength: H₃AsO₃ (9.22) <H₂SO₃ (1.9)<HMnO₄(-2.25)< H₂SO₄(-3)

                       (b) HClO(7.53)< HClO₂ (2)< HClO₃ (-1)< HClO₄ (-10)

Q10 (a) H₂O > NH₃ > PH₃ (higher the electronegativity, higher will be the hardness)

(b) NH₃ > OH^-> NO₂^- (hardness is decreases with increase in electron density)

(c) the h= ½ (I-A), more is the difference between ionization energy and electron affinity, more will be the hardness.

Q11. (a) The strongest Bronsted base acid: TeH₂ (lowest in oxidation number)

(b) NH3 is the strongest base (smallest in size)

(c) strongest that will react with H+ will be (CH₃)₂NH :order of basicity of amines: (CH₃)₂NH > (CH₃)₃N > CH₃NH₂ > NH₃

Q12 (a) As S^-2 is softer base than OH^-, so OH^- will precipitate with M⁺³ as M(OH)₃

(b) As O^-2 is harder base than S^-2, so will precipitate with M⁺³

(c ) Cu⁺² will form precipitate with NH₃, as NH₃ is harder than OH^-

(d) Ag⁺ will form precipitate with NH₃, as NH₃ is harder than PH₃

(e) CO is a soft base so will bind more strongly with Fe