ii). 6 iii). 10? c). The mercuric ion, Hg2+, has a high affinity for chloride: Hg2+ + 4Cl– HgCl42–, for which the formation constant is Cl = 3.98  1015. For a solution containing 0.5 mol L-1 total chloride and 5.00  10-3 mol L-1 total EDTA, determine the fraction of Hg existing as the free ion, as the tetrachloride anion, and as the EDTA complex, at a pH of i). 2 ii). 6 iii). 10 [You should assume that the total metal ion concentration is much less than 0.05 mol L-1.] d). An amalgam is known to contain only mercury, sodium, and calcium. 5.218 grams of the sample is treated with an appropriate oxidizing agent, and made up to 500 mL. 25 mL aliquots of this solution, buffered to pH = 2.6, are titrated against a 0.0122 mol L-1 MgY2– solution: the mean titre value obtained is 44.19 mol L-1. When 10 mL aliquots are buffered to a pH of 9.5, a titre value of 57.43 mol L-1 is obtained. Determine the percentage by mass of the mercury, sodium, and calcium in the amalgam. PROBLEM 22. Greenhouse gas emissions are a topic of global environmental concern. The increase in atmospheric concentration of one greenhouse gas, CO2, has been over the past several decades. a). Let us approximate the distribution of greenhouse gases in the Earth's atmosphere by assuming that these gases (CO2, H2O vapour etc) are localized within a layer between the altitudes of 10 and 11 km. [Such a description is not accurate, but serves to illustrate some concepts.] What is the effect of such a greenhouse-gas layer upon the temperature of the atmosphere at an altitude of 5 km? b). What is the layer's effect on atmospheric temperature at 15 km? Explain, qualitatively, this 'side-effect' of the Greenhouse layer. c). How does temperature change in the lower atmosphere influence the equilibria of CO2 and of H2O between the gaseous and aqueous phases? Will a shift in the
The most acidic species will be A, which has the fluorine  to the carboxylic acid (maximum stabilization by F) and has no alkyl sidechains (minimum destabilization by methyl groups). The least acidic of the optically-active species is H, which has the fluorine  to the COOH group (minimum inductive donation from F to COO–) and which also has a methyl group  to the COOH (maximum inductive withdrawing from COO–). d). This reaction produces an ester: R–COOH + R'–OH R–COO–R' + H2O e). The labelled ester is: The reaction occurs as nucleophilic attack of the carboxyl carbon: f). i). The expected product is ii) When ethanoic acid is added to the NaOH solution, an acid-base equilibrium is established: CH3CO*OH + OH– CH3(COO*)– + H2O The ethanoate anion has two equivalent oxygens. When the solution is the label is scrambled: CH3(COO*)– + D+ with the two isotopomers formed in equal amounts (provided that the ethanoic acid / hydroxide system had sufficient time to attain equilibrium). The former isotopomer will yield the same product as i); the latter will give unlabelled propyl ethanoate and labelled water (or, to be more precise, labelled HOD). PROBLEM 17. a). The volume of a sphere is V = (4/3)  r3. r = 3.5 x 10-10 m, so V = 1.796  10-28 m3. Now for the pressure: PV = nRT, so P = nRT / V. n = 1 atom = (6.02205  1023)-1 = 1.661  10-24 moles. so P = 2.2907  104 kPa (i.e. 229 atmospheres)