The pKa of bromocresol green is around 4.7.
Bromocresol green become yellow in acidic solutions.
To prepare bromocresol green indicator, dissolve 0.1 g of bromocresol green in 100 mL of ethanol. For methyl red indicator, dissolve 0.1 g of methyl red in 100 mL of ethanol. Store both indicators in a tightly sealed container away from light.
Bromocresol green changes color in the pH range of 3.8 to 5.4, which is close to the pH at the endpoint of the titration of hydrochloric acid with sodium tetraborate. This makes it a suitable indicator for this titration as it changes color around the equivalence point.
By definition, the pKa of a weak acid is the pH at which the concentrations of the acid and its conjugate base are equal. In this case, since the solution is yellow (acid) and blue (base) at pH 4.68, it means that the concentration of the acid and base forms of the indicator are equal. Therefore, the pKa of bromcresol green is 4.68.
Titration with strong base requires eg. methyl red, changing to yellow at 6.2, but it endpoint may come too early when the sulfonic acid is weaker than acetic acid: OK if pKa < 4.5 .So it's safer to use phenolphaleine (purple at pH=8.5) for acids with pKa < 8
Bromocresol green become yellow in acidic solutions.
To prepare bromocresol green indicator, dissolve 0.1 g of bromocresol green in 100 mL of ethanol. For methyl red indicator, dissolve 0.1 g of methyl red in 100 mL of ethanol. Store both indicators in a tightly sealed container away from light.
One way to separate bromocresol green and methyl red is by using paper chromatography. The two compounds can be spotted onto a piece of chromatography paper and allowed to separate in a solvent. The different solubilities of the compounds will cause them to migrate at different rates, allowing for their separation.
Examples: turmeric, methyl red, bromocresol green.
Bromocresol green changes color over a pH range of 3.8 to 5.4, making it suitable for acidic to neutral pH ranges. It has a distinct color change from yellow to blue, which is easily visible to the naked eye. Additionally, it is stable and has a long shelf life.
Bromocresol green changes color in the pH range of 3.8 to 5.4, which is close to the pH at the endpoint of the titration of hydrochloric acid with sodium tetraborate. This makes it a suitable indicator for this titration as it changes color around the equivalence point.
Bromocresol green changes color over a broader pH range (3.8-5.4) than phenolphthalein (8.2-10.0), leading to a different endpoint in titration. This difference in color change can result in slightly different titer values when using the two indicators.
By definition, the pKa of a weak acid is the pH at which the concentrations of the acid and its conjugate base are equal. In this case, since the solution is yellow (acid) and blue (base) at pH 4.68, it means that the concentration of the acid and base forms of the indicator are equal. Therefore, the pKa of bromcresol green is 4.68.
Titration with strong base requires eg. methyl red, changing to yellow at 6.2, but it endpoint may come too early when the sulfonic acid is weaker than acetic acid: OK if pKa < 4.5 .So it's safer to use phenolphaleine (purple at pH=8.5) for acids with pKa < 8
The pKa of diisopropylamine is around 10-11.
Methyl Red, methyl orange, bromophenol blue, phenolphthalein, thymolphthalein, bromocresol green, bromothymol blue are all used as acid base indicators.
The pKa of bromoacetic acid is approximately 2.64.