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Quiz06 - Physical Chemistry(I Quiz 06 Dec 27 2007 1(15 For...

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Physical Chemistry (I) Quiz 06 Dec. 27, 2007 1. (15%) For a solvation reaction, both H 2 and Cl 2 gases dissolved in aqueous solution to formed solvated ( ) aq H + and ( ) aq Cl - ions. Given the following information to calculate 0 f H Δ , 0 f G Δ and 0 S for ( ) aq H + (5%) and ( ) aq Cl - (10%). 0 1 167.2 kJ mol r H - Δ = - , 0 1 131.2 kJ mol r G - Δ = - , 0 1 1 2 ( , ) 130.7 J mol K S H g - - = , 0 1 1 2 ( , ) 223.1J mol K S Cl g - - = . 2. (15%) Derive solvation G Δ o based on Born model (10%) and explain why it is not appropriate to use ionic radii from crystal structures to calculate of ions (5%)? 3. (10%) Express μ ± in terms of μ + and μ - for MgBr 2 and Li 3 PO 4 . Assume complete dissociation. 4. (10%) Calculate the mean ionic activity of a 0.0150 m K 2 SO 4 solution for which the mean activity coefficient is 0.465. 5. (25%) For the Debye–Hückel limiting law (DHLL), 2 2 2 1 1 1 0 0 ln | | | | where ( ) 8 j j m j r r q N I e z z A z z kT kg L mol kg kT V ± + - + - - - = - = - = ρ κ γ κ πε ε ε ε (a) work out the numerical constant A for calculating ln γ ± (15%); (b) using DHLL to estimate the value of γ ± in 0.01 m solutions of H 2 SO 4 (aq) involving 0.02 m HCl(aq). (10%). 6. (15%) In the Debye–Hückel theory, the counter charge in a spherical shell of radius r and thickness dr around the central ion of charge + q is given by 2 . r q re dr κ κ - - Calculate the most probable value of r , r mp , from this expression (10%). Evaluate r mp for a 0.050 m solution of NaCl at 298 K (5%).

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