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3. Answer ALL parts (a) to (h). (a) Compare the acidity of the two aqueous oxoacids tabulated below and give reasons for the difference in pKa values at 298 K. [Word limit=100] [4%] OH 0= OH nitrous acid pka = 3.3 nitric acid pka = -1.4 (b) Calculate the pH of an aqueous nitrous acid (HNO₂) solution of concentration 0.20 mol dm-³. Justify any assumptions made in your calculation. The dissociation constant, K₂, for nitrous acid is 4.7 x 104 at 298 K. [4%] (c) Calculate the pH of an aqueous buffer solution containing 0.20 mol dm-³ nitrous acid and 0.40 mol dm-³ sodium nitrite (NaNO2) at 298 K. State any assumptions that you make in your calculation. [3%] (d) Silver bromide, AgBr, is a sparingly soluble salt in water. Write down expression for the solubility product, Ksp, of silver bromide. [1%] (e) Calculate the molar solubility of AgBr in water, given that Ksp = 5.0 x 10-13 at 298 K. [2%] (f) Consider the gas phase reaction between nitrogen and hydrogen, forming ammonia. In a sealed reaction chamber the system exists in dynamic equilibrium. Experimental measurements performed at 450 K show that the reaction is exothermic. 450 K N2 (g) + 3 H2(g) 2 NH3(g) (AH, = -92 kJ mol-¹) 1 atm Write an expression for the equilibrium constant, K. You may use either the gas concentrations (mol dm-³), or partial pressures (bar), when forming this expression. [2%] (g) Predict the change in the position of equilibrium if the temperature of the reaction vessel is raised to above 450 K. [2%] (h) Predict the change in the position of equilibrium if the total pressure inside the reaction vessel is increased. [2%]