The pKa can be determined from the spectrophotometric data using different methods. Molecular Weight 646.36 . Bromothymol blue is an acidic pH chromoionophore where acid to base change corresponds to its neutral to anionic form, respectively. Ensure that the solutions are mixed well. There is a linear relationship between log ( [ln-]/ [Hln]) and pH. Chloroform showed the highest affinity for bromothymol blue, followed by methylene chloride, ethylene dichloride, benzene, toluene, and carbon tetrachloride. Solutions of different concentration of the indicator were used. The pKa′ value was determined using a method similar to that of Reilley and Swayer. EC Number 252-169-7. Description: Bromothymol Blue (BTB) is a pH indicator (pKa approx. 2 Answers. Beilstein/REAXYS Number 6887926 . Empirical Formula (Hill Notation) C 27 H 27 Br 2 NaO 5 S . Computational methods, such as SQUAD (84) 16 and SPECFIT/32, and some new methods As a pH indicator,bromothymol blue, for example, would be useful between from about pH6.0 to pH 7.6. Anonymous. Acid - Base indicators are either weak acids or weak bases so they exist as molecules in equilibrium with their ions. Meloun et al. In this experiment, spectrophotometry is employed to measure the pKa of bromothymol blue, an acid-base indicator. Answer Save. NACRES NA.47 1 decade ago. Favorite Answer. Using bromothymol blue you wouldn't be able to distinquish between anacid with pH 4 from an acid with pH 5. It shows that pH=pKa where [ln-]= [Hln] or hwere ( [ln-]/ [Hln])=1 or where log ( [ln-]/ [Hln])=0. PubChem Substance ID 24892083. ,IC10113005EA,IC10113025EA. Spectrophotometric determination of the pKa of Bromothymol Blue. [10] [11] describe multiwavelength analysis and nonlinear least squares regres-sion methods. Explain why the acid - base indicator bromothymol blue turns yellow when added to dilute HCl but blue when added to dilute NaOH. pH = pKa - log ( [HIn] / [In-] ) … (2) Assume a cuvet with a 14.45 mm diameter was used. Determination of the pK_a of Bromothymol Blue Use the following graph to determine the molar absorptivity of Bromothymol blue (BTB)? Supplier: MP Biomedicals. MDL number MFCD00077263. Bromothymol blue, Powder ACS. They would both appearyellow. Molar absorptivity ___ (You will be using this value in your experiment.) Given the equation: y= 48048x- 0.0105, find the molar absorptivity and use this value in your experiment. Into each of the cuvettes place 3 mL of the solutions of the various pH values (hydrochloric acid, the buffer solutions with pH values 6.0, 7.0 and 8.0, and sodium hydroxide solution). Place three small drops of bromothymol blue solution into each of the 5 cuvettes. 2. The indicator (HIn) is a monoprotic acid and we can represent its dissociation as follows: HIn → H+ + In- … (1) The equilibrium expression for such dissociation can be written as. Relevance. Other indicators work in different pH ranges. Bromothymol Blue sodium salt powder Synonym: 3′,3′′-dibromothymolsulfonephthalein sodium salt CAS Number 34722-90-2. Indicator: pH Range: pKa: Acid Form: Base Form: Methy Violet: 0.0 - 1.6: 0.8: Yellow: Blue: Thymol Blue: 1.2 - 2.8: 1.6: Red: Yellow: Methyl Yellow: 29. For this reason it can be electrostatically immobilized on the surface on anion-exchanger resin like Amberlite IRA 401. 7.1) that is used as a biological slide vital stain to define cell walls or nuclei under the mic... SDS. Either weak acids or weak bases so they exist as molecules in equilibrium with their ions indicator, bromothymol,. Methylene chloride, ethylene dichloride, benzene, toluene, and carbon tetrachloride under mic... 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