27 Jan, 2012
Introduction: A popular technique in separating components of a mixture is paper chromatography. We use paper chromatography to separate mixtures and isolate there components to collect them individually. In this experiment, we will use acid- base indicators to help determine the unknown mixture. Acid- base indicators will change in color when the presence of pHs rise and fall when acids or bases are added to a solution. After setting strips of paper into a flask with the eluding solvent and waiting 45-60 minutes, we will set the strips over Ammonium hydroxide. Ammonium hydroxide serves as a developer for the components and brings out there color at a high pH. We will measure the distance from the center of the band to the point where the indicator was applied and measure the distance of the solvent front to the point of appliance. We will use the data to help determine the unknown identity of the mixture from a list of acid- base indicators. Abstract: The identity of the unknown mixture was determined by the methods paper chromatography and calculating the Rf values. Bromthymol Blue Rf value was determined to be 0.96 and the unknown mixture Rf value was 0.94 cm. Bromcresol purple Rf value was 0.36 and the unknown mixture Rf value was 0.34 cm. Phenol red Rf value was 0.23 and the unknown mixture Rf value was 0.15 cm. Based on the results, these three acid-base indicators are the identities of the unknown mixture.