1 / 6

pH Indicators and Color Changes in Acid-Base Titration

Learn about the role of bromthymol blue and bromcresol green in acid-base titrations, including the color changes at different pH levels. Also explore the existence of pink and blue cobalt complex ions in a solution.

josephilewis
Download Presentation

pH Indicators and Color Changes in Acid-Base Titration

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Eq Rxn: HIn  H+ + In-or HB  H+ + B- • When bromthymol blue (pKa=7) is used for the titration of an acid, the starting form will be HIn (yellow), and the color change occurs at a pH of about 6. When used for titration of base, the starting form is In- (blue), and the color change occurs at a pH of about 8. Thus, the useful pH for bromthymol blue is pKa +/- 1 = 7 +/- 1 (Ref Zumdahl p714)

  2. Eq Rxn: HIn  H+ + In-(or HB  H+ + B- ) yellowblue

  3. Eq Rxn: Cu2+(aq) + 4NH3(aq) <==> [Cu(NH3)4]2+(aq) blue CuSO4 colordeep blue

  4. [Co(H2O)6]2+(aq)+4Cl-(aq)+heat[CoCl4]2-(aq)+6H2O(liq)pink blue Is it possible for both the pink and blue cobalt complex ions to exist in the solution at the same time? Yes, in an equilibrium all species are present. The conditions determine the predominant form (species in higher concentration).

  5. [Co(H2O)6]2+(aq)+4Cl-(aq)+heat[CoCl4]2-(aq)+6H2O(liq)pink blue Check if you can predict results interactively at: http://www.chem.uiuc.edu/webfunchem/cobalt/cobaltindex.htm

  6. Solubility of Carbon Dioxide in water CO2(g)  CO2(aq)+H2O  H2CO3(aq)  H+(aq) + HCO3-(aq) Bromcresol green (BCG) indicator pKa = 4.8 HIn  H+ + In- Since BCG forms a colored complex with albumin (protein), it is also used as a dye binding agent for the quantitative analysis of albumin in human serum.

More Related