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Question

a. Consider the following equilibrium: PCl3 (g) + Cl2 (g) ----> PCl5 (g) ∆H= –92kJ Suppose this reaction is at equilibrium. Identify all possible disturbances (external stresses) that would result in the formation of more PCl5 by applying LeChâtelier’s principle. 

b. A solution of vanillic acid is prepared by dissolving 0.300 g of vanillic acid(HC8H7O4, M= 168.1g/mol) in enough water to make 250.0 mL of solution. Determine the molarity of vanillic acidin this solution

Answer 1

 PCl3 (g) + Cl2 (g) ----> PCl5(g) + heat

(a) Disturbances to result in more PCl5:

..Remove PCl5

..Add PCl3

..Add Cl2

..decrease pressure

..lower temperature

(b) moles acid = 0.300 g x 1 mol/168.1 g = 0.001785 moles

Molarity = 0.001785 mol/0.25 L = 0.00714 M (3 sig. figs.)