chemistry prac 1

Question 1 a) Write down the overall equation showing the formation of [Fe(acac)3] from [Fe(H2O)6]3+ and acetylacetone (equation 4.3 in the Introduction).

b) What reagent do you weigh out that ends up being the source of the [Fe(H2O)6]3+?

Question 2 a) Circle the correct word in bold text to complete the following statements: A pH of less than 7 means a solution is acidic/basic. A pH of greater than 7 means a solution is acidic/basic.

b) The equation showing acetylacetone, acacH, forming the acac¯ ion is below: acacH acac¯ + H+ What is it about this equation that results in a solution of acacH being slightly acidic?

c) Given that sodium acetate is a base (remember that sodium acetate can be considered as sodium ions and acetate ions), complete the following equation showing the reaction of acetate ions with H+:

CH3COO– + H+

Question 3 a) What is the connection between the two equations below?

acacH acac¯ + H+ [Fe(H2O)6]3+ + acac¯ [Fe(H2O)4(acac)]2+ + 2H2O

b) Using your answer to Question 3(a), explain why the pH of a mixture of [Fe(H2O)6]3+ and acacH (solution 2, Table 4.1) is lower than a solution of either of the components by themselves.

c) Explain why the pH increases on addition of sodium acetate (solution 3, Table 4.1) d) Therefore, explain why more [Fe(acac)3] is produced after the addition of sodium acetate. (Hint: use Equation 4.3 and Le Châtelier’s Principle.)

Question 4
a) Steps 1 and 2 in the PROCEDURE describe test tubes A and B in Diagram 1. Test tube A should contain the neutral [Fe(acac)3] complex synthesised in Part One and polar water, test tube B should contain [Fe(acac)3] and non-polar dichloromethane. Using the idea of “like dissolves like”, which test tube – A or B – do you predict will contain the dissolved [Fe(acac)3]? (Hint: see the notes on solubility in the Introduction section for help.)

b) If the intensity of the colour of the solutions can be taken as a rough guide as to the concentration, which solvent layer in test tube B, the top or the bottom, contains the most [Fe(acac)3]?

c) Is the layer you chose in question 4 (b) the polar (water) layer or the non-polar (dichloromethane) layer?

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