Chem H.W.

 Chem H.W.

     

__________________________________ Section: ___________ Date: ____________

Experiment 5: EXPERIMENTS IN CHEMICAL EQUILIBRIUM

PART 2: Determination of an Equilibrium Constant (Laboratory Report)

Table 1 – DATA: Titration of Stock Hydrochloric Acid

(each partner use his/her own data here)

Trial 1 Trial 2 Trial 3 Trial 4

-Concentration of standard NaOH (M) 1.0 M 1.0 M 1.0 M 1.0 M

-Initial volume reading (mL) 10 ml 19 ml 10 ml 9 ml

-Final volume reading (mL) 22. ml 35. ml 22. ml 20. ml

-Volume of standard NaOH

used (mL)

12 ml 16 ml 12 ml 11 ml

-Moles of NaOH used

= moles HCl in 5.00 mL HCl solution

-Average of last 2 trials (see text)

To Table 3 (2)

-Mass of HCl in 5.00 mL HCl solution

-Mass of 5.00 mL HCl solution

(d = 1.05 g/mL)

-Mass of H2O in 5.00 mL HCl solution

-Moles H2O in 5.00 mL HCl solution

To Table 3 (1)

Table 2 – DATA: Titration of Equilibrium Mixtures

(use both partners’ data here)

BottleA1 BottleA2 BottleB1 BottleB2 BottleC1 BottleC2

-Initial volume reading (mL) 10 ml 10 ml 10 ml 10 ml 10 ml 10 ml

-Final volume reading (mL) 47 ml 46 ml 45 ml 44 ml 43 ml 42 ml

-Volume of standard NaOH 37 ml 36 ml 35 ml 34 ml 33 ml 32 ml

used (mL)
-Moles of NaOH used

= total moles HCl plus HAc

-Average total moles of HCl

plus HAc. To Table 3 (3)

Table 3 – CALCULATIONS: To Find Equilibrium Constant

Flasks A Flasks B Flasks C

Initial moles of EtAc

Initial moles of pure H2O added

Initial moles of H2O added with HCl (1)

Initial total moles of H2O

Equilibrium moles of HAc

plus HCl (3)

Moles of HCl (2)

Equilibrium moles of HAc

Equilibrium moles of EtOH

Equilibrium moles of EtAc

Equilibrium moles of H2O

Equilibrium constant *

Average equilibrium constant, Keq

*hint: make an ice table…

Supplementary Questions

1. What is the average % deviation of your Keq values (see Chem 206 Exp.1A for a

reminder of % deviation)? List three sources of experimental error that are likely responsible

for this variability.

2. Based on your average value of the equilibrium constant, does the equilibrium

favour the formation of the products ethanol and acetic acid, the starting reagents, or neither?

3. Suppose you stoppered the flasks after your titrations to determine the equilibrium

constant and kept the solutions for another day so that equilibrium was re-established. What

would happen to the amount of ethanol present? What would be the relationship of the original

equilibrium constant you calculated to the new one?

4. Would the results of this experiment have been affected if you had forgotten to add

the hydrochloric acid to the reaction bottles? Why or why not?