this equilibrium and therefore changes in colour of the solution from

This equilibrium and therefore changes in colour of

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this equilibrium and therefore, changes in colour of the solution from colourless clear to opaque brown to colourless clear. In other words, the shifting and adjustment of the equilibrium of the solution as the concentrations of certain species are changed. Reaction observed: 2H + (aq) + CO 3 2- (aq) H 2 CO 3 (aq) H 2 O (l) + CO 2 (g) (g) Change observed after adding 3 drops (0.15mL) 0.1M HCl: solution changes from clear, colourless to opaque, cloudy white. Combination reaction between Ag + (aq) ion and Cl - (aq) ion which produces AgCl(s) causes the cloudy white solution. The precipitate is formed due to the reason that Ag + (aq) and Cl - (aq) are insoluble when combined to form AgCl. Reaction observed: Ag + (aq) + Cl - (aq) AgCl(s)
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(h) Change observed after adding 3 drops of NH 3 (aq): The solution returns to being clear from being cloudy white. A synthesis reaction between Ag + (aq) ion and 2NH 3 (aq) produces [Ag(NH 3 ) 2 ] + (aq) that causes the colour change observed. Reaction observed: Ag + (aq) + 2NH 3 (aq) [Ag(NH 3 ) 2 ] + (aq) 2. Yes, same changes are observed when Step 7 and Step 9 are repeated due to Le Chatelier's principle being in action during the shifts in equilibrium. The equilibrium, being dynamic, seeks to balance itself in response to changing concentrations of different species of acids and bases and buffers. (i) The solution ’s colour turns from clear to opaque, yellow -white. The combination reaction between Ag + (aq) and I - (aq) forms an equilibrium with AgI(s) which in turn produces the colour change observed. The formation of the precipitate is due to the fact that Ag + (aq) and I - (aq) are insoluble when combine. The K sp being very low: 8.52 × 10 -17 . Reaction observed: Ag + (aq) + I - (aq) AgI(s) (j) The solution’s colour changed from opaque, yellow-white to opaque, dark brown along with some observable black precipitate. Ag 2 S(s) causes such colour change as it is produced in the combination reaction between Ag + (aq) and S 2- (aq) that are insoluble when combined due to a very low K sp of 8.0 × 10 -51 . Reaction observed: 2Ag + (aq) + S 2- (aq) Ag 2 S(s) Limitations of Part 2: Using dropwise measurements required attention to detail in when the solution truly changed in qualitative characteristics. Many times, one or more drops were added after the change occurred. This causes a change in concentrations; however, the equilibrium should remain constant. Buffer Solution and blood pH (k) The pH of distilled water is 6.01. It is slightly more acidic than the expected value of 7.00 which interprets that distilled water, when in constant pressure and therefore, in contact with air, is acidic. This acidity is due to absorption of some of CO 2 that is present in the air and the instance that distilled water is different in composition from normal water. Normal water contains certain minerals and impurities which adjust its pH close to neutral. Whereas distilled water, does not contain those minerals and impurities and therefore, possesses a lower pH than normal water. Also, it is possible that the process of CO 2 diffusing into the distilled water may form carbonic acid and contribute to the lowering of the pH with the aid of magnetic stirring.
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  • Fall '14
  • Pell, Wendy

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