Label one pitcher as base, and fill completely with base solution.40 mL) in a small plastic bottle and place these in back of each of the beakers. Place a premeasured amount of acid/alcohol mixture (ca.Set them on the light background in rainbow order (ROYGBV) from left to right. Label the beakers with their color, and place five drops of indicator solution of that color in the center of each beaker.Mix 1.00 g of NaOH with distilled water, dilute to 2.0 L, and transfer to a plastic pitcher.
Dilute 10 mL of concentrated H2SO4 in 20 mL of glycerin, and transfer to a dropping bottle.Mix with an equal volume (1 L) of 95% ethanol. Dilute 2.8 mL of concentrated H2SO4 to 1 L with deionized water.Mix the amounts listed above with 30 mL 95 % ethanol and store in dropping bottles labeled with the color indicated.Īcid-alcohol solution (0.05 M H2SO4 mixed with an equal volume of 95% ethanol):
VIOLET: 0.9 g phenolphthalein + 0.4 g thymolphthalein. GREEN: 0.6 g thymolphthalein + 6.0 g p-nitrophenol. ORANGE: 0.45 g phenolphthalein + 6.0 g p-nitrophenol. RED: 1.5 g phenolphthalein + 3.0 g p-nitrophenol. 
2 L pitchers (2 identical, non-transparent). 600 mL Berzelius, tall form beakers (6). light background such as white table cover. Then the contents of the beakers are poured into the large glass container where a few drops of viscous acid solution have been previously placed, causing the resulting solution to become acidic and converting the indicator back to its colorless form. Adding more base to each beaker causes the colors to reappear. The dense droplets sink and are then dispersed by stirring, neutralizing the base and converting the indicator to its colorless form. Then several drops of viscous acid solution are added to each beaker. With the second addition of NaOH solution, an excess of base results, the solutions become alkaline, and the indicators become colored. The initial addition of sodium hydroxide solution is not enough to neutralize the acid present, and the indicators remain colorless. Because the contents of the beakers are acidic, the indicators are colorless. The indicator solutions used are very concentrated, more concentrated than standard indicator solutions, producing intense solution colors.Īt the start, each beaker contains one of the six rainbow color indicator solutions along with the acid/alcohol mixture. Because these colors are close to the three primary colors, virtually any color of the rainbow can be produced by some combination of these indicators in basic solution. The three indicators used are all colorless in acidic solution, but each produces a different color in basic solution. This demonstration shows that a mixture of indicators can produce a color change different from that obtained with the individual indicators, resulting in the colors of the rainbow appearing and disappearing. The colored solution beakers are then mixed in a large container resulting in the colors disappearing once again.Ī number of objectives are satisfied with this presentation, including a) demonstrating color changes of solutions due to changes in pH of the solutions, b) demonstrating the reversibility of indicator color changes, c) providing an introduction to acid/base chemistry, d) getting students to think about how acids and bases interact, and e) providing an introduction to standard indicators. The colors disappear and reappear when other colorless liquids are added to the beakers. When a colorless liquid is poured into six beakers, the liquid in each beaker turns a different color of the rainbow.
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