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Why did the phenol red turn pink over time?
Phenol red is yellow under acidic conditions (high H ion concentration), pink under basic or alkaline conditions (low H ion concentration) and orange under neutral conditions. If the CO2 concentration decreases, the H ion concentration will also decrease and the solution will change to pink, becoming basic.
At what pH does phenol red turn pink?
pH 8.1
Phenol red is a water-soluble dye used as a pH indicator, changing from yellow to red over pH 6.6 to 8.0, and then turning a bright pink color above pH 8.1.
What color does phenol red turn under light?
Hopefully! Hypothesis: If photosynthesis occurs (with light), then pH will increase as CO2 is removed, and Phenol Red will turn from yellow to red.
Why did the solution containing phenol red and Elodea change from yellow to red?
The half yellow phenol red having an Elodea twig changes back its color to red because Elodea performs photosynthesis and removes CO2 from the solution. The other half keeps its red/pink color. Conclusion – Photosynthesis uses CO2 to synthesize glucose. 5.
What waste does bacteria produce to show a yellow color change in phenol red?
In this exercise you perform a test for urease production. The test medium contains urea and the dye phenol red, a pH indicator. If the bacteria produce urease, there will be a positive test reaction, and the color of the medium will change from yellow to cerise.
How does phenol red change from yellow to red?
Its color exhibits a gradual transition from yellow (λmax = 443 nm) to red (λmax = 570 nm) over the pH range 6.8 to 8.2. Above pH 8.2, phenol red turns a bright pink (fuchsia) color.
Why does phenol turn orange in a tube?
Sometimes an orange color will develop in the tube, this represents a pH > 6.8 and should not be considered positive. Also be catuious of tubes that inititally produce acid then turn red or pink as nitrogenous products are produced. This type of reaction is characteristic of oxidative, not fermentative metabolism.
Why does phenolphthalein turn pink when the pH is high?
TL;DR (Too Long; Didn’t Read) Phenolphthalein turns pink when exposed to substances above a pH of 8.2- and becomes purple at even higher pH values. This color change is a result of ionization, which alters the shape and charge of phenolphthalein molecules.
Why is the phenol red in the carbohydrate test?
Positive: After incubation the liquid in the tube turns yellow (indicated by the change in the color of the phenol red indicator). It indicates that there is drop in the pH because of the production of the acid by the fermentation of the carbohydrate (sugar) present in the media.