Chemistry: equilibrium and lechatelier’s principle

These are practical questions to be done in lab, for writing a solution/calculation with no values/experimental results please make an educated guess because the prac is yet to be done. For the other questions please try to be as specific as possible. Read the document I uploaded (it has procedures and other useful material). Cheers.

Question 1

a) Write down the overall equation showing the formation of [Fe(acac)3] from [Fe(H2O)6] 3+ and acetylacetone [Fe(H2O)6] 3+(aq) + 3acacH(aq) [Fe(acac)3](aq) + 6H2O(l) +3H+ (aq).

b) What reagent (chemical agent) 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 is lower than a solution of either of the components by themselves.

c) Explain why the pH increases on addition of sodium acetate.

d) Therefore, explain why more [Fe(acac)3] is produced after the addition of sodium acetate. (Hint: use the Equation [Fe(H2O)6] 3+(aq) + 3acacH(aq) [Fe(acac)3](aq) + 6H2O(l) +3H+ (aq)  and Le Châtelier’s Principle.) (refer to the document for the principle).

Question 4: [Pg 11 on the document, also need to scroll back to Part 1 to answer this]

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?

Question 5

a) Complete the equations that describe the stepwise formation of the tris-acac iron complex, [Fe(acac)3]:

1)                                      [Fe(H2O)6] 3+ + acac¯        =>       [Fe(H2O)4(acac)]2+ + 2H2O

2)                                      _________________         =>       ______________________

3)                                      _________________         =>       [Fe(acac)3] + 2H2O

For questions 5 b, and question 6, refer to the word document.

Goodluck.