The mixed bromothymol blue solution will turn yellow in an acidic solution and blue in basic solutions. Add 0. Dilute the mixture with 1 L of distilled water in a large container.
The solution should be dark blue in color. If the solution appears green, use a pipette to slowly add sodium hydroxide drop by drop to the solution until it changes to blue. Sodium hydroxide is a corrosive chemical. Be sure to wear all safety gear, including gloves and goggles. Thus, it can be either in a deprotonated form or protonated form, by appearing blue or yellow, respectively. It is also a bright aquamarine by itself and greenish-blue in a neutral solution. This neutral form deprotonation results in a structure of highly conjugated, considering for the color difference.
A deprotonation intermediate mechanism is responsible for the greenish color in the neutral solution. The bromothymol blue's protonated form has its peak absorption at nm, therefore transmitting yellow light in the acidic solutions. In contrast, the deprotonated form contains its peak absorption at nm, thereby transmitting the blue light in many basic solutions. Besides, the Bromothymol blue of highly acidic is magenta in color. The bromothymol blue's general carbon skeleton is common to most of the indicators, including thymol blue, bromocresol green, and chlorophenol red.
The presence of a single moderate electron-withdrawing group which is a bromine atom and two moderate donating groups which are alkyl substituents are completely responsible for the active indication range of bromothymol blue from a pH value of 6. While the conjugation is responsible for the nature of the color change range and length, these substituent groups are ultimately responsible for the active range of the indicator. Bromothymol blue indicator is sparingly soluble in oil but soluble in ether, water, and alkalis' aqueous solutions.
It is also less soluble in nonpolar solvents, including toluene, benzene, and xylene, and it is practically insoluble in the petroleum ether. Let us look at some of the physical properties of bromothymol blue. Covalently-Bonded Unit. Your teacher should be able to direct you here - the most important thing is to first isolate that ONE variable you are testing -- if you don't - your results will be confusing and hard to analyze.
Re: How to use Bromothymol Blue Post by student22 » Mon Jan 13, pm You have brought up several points that hadn't come to my attention yet. Like you said, how exactly do I know when to stop the clock when watching the color change?
Could you please explain to me what you have done in your previous classes? Looks like I have a good amount of work ahead of me to make sure that I am only testing for one variable. I may have to rethink several things to make my results more accurate. Suppose I gather volunteers of relatively the same body frame and condition height,weight,health etc.
Would that specify it enough to perform a justified experiment, or am I still exposed to too many alternate variables. Like you said, I will consult my teacher tomorrow when I see her in school. At this point of the project having already submitted my objective and a brief research paper , I may not be able to completely rework my experiment, however I'm pretty sure she can direct me to a solution.
Thanks again for your advice. Re: How to use Bromothymol Blue Post by yvetteds » Mon Jan 13, pm In my class, we were using the BB experiment as a way to compare the change in metabolism by the amount of carbon dioxide the body produced as a waste product comparing a group at rest the control to the experimental group after exercise.
It was not an in depth data analysis - but we did find that after exercise the average amount of time it took to change the BB from blue to yellow was shorter more carbon dioxide being exhaled from each breath when subjects stopped exercising.
But then again, this was a class demonstration - and there were probably more variables we needed to control if this was to be a reliable science fair project. I am hoping your science teacher can give you more specific directions since I don't know the level of work she expects - or the requirements you're expected to achieve. The hardest part of any science project is as you are finding out - how to control for just one variable - so that when you do get data to analyze, that the change you see is due to just the one thing you changed and not to some interfering variable.
Even the food the person ate before your experiment will change the results. So, when using human subjects it's really a challenge to control for all the variables necessary. That is not to say this is impossible - you might look up information under Sports Medicine - since that is where a lot of research is being done on how the body reacts and uses fuel - I am assuming you have had some background on basic cell respiration?
If so, then you will probably find exercise research interesting as far as lung capacity and what you are trying to show.
Some questions to think about - Does a person's 'fitness' affect how fast they exhale carbon dioxide after exercise? That was one question that came up in our classes when we were trying to analyze the results. But all the questions you think of along the way - once you start your basic project can be incorporated into your discussion and analysis and 'further investigation'. That's the purpose of research - to uncover more questions - one step at a time. I have tried using salt in the distilled water but it still ends up yellow.
What am I doing wrong?
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