CHM 111 Lab Investigation: Acid and Base Analysis What are the identities of the
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Question
CHM 111 Lab Investigation: Acid and Base Analysis What are the identities of the unknown chemical solutions? than hydroxide ions in solution. Introduction. Acids have a pH below 7 and have a higher concentration of hydronium ions Bases have a pH above 7 and have a higher hydroxide ion concentration than hydronium neutralize one another to form water and a salt. When equal moles of a strong acid and a strong base each other up and form a neutral solution, which has a pH of 7. Indicalors can used to determine the solution. dark pink on. When acids and bases react they react they completely use approximate pH of a The Task Your goal is to identifly the unknown chemical solutions by systematically reacting them together in the same test tube The four unknowns are water, 0.1 MHCI (ag). 0.1 M NaOH (ag), and phenolphthalein. You need to decide which unknown solution has which chemical identity The guiding question of this investigation is: What are the identities of the unknown chemical solutions? Materials. You may use any of the following materials during your investigation: Equipment Consumables . Test tube Unknown A Unknown B Unknown C . Unknown D Stirring rd Safety Precautions. Students need to wear goggles, long pants, closed toe shoes, and a shirt with sleeves. All waste should be disposed of in the inorganicionic waste container Getting Started. Before you can design and carry out your investigation, you must determine what type of data you will need to collect, how you will collect it, and how will you analyze it. You need to fill out the investigation proposal before starting To determine what type of data you need to collect think about the following questions: What type of observations will allow you to distinguish between the unknown chemicals? What does it mean if the solution is pink? if it is clear? . . To determine how you will collect your data, think about the following question How can you systematically react the unknown chemicals in order to find distinguishing observations? . In order to determine how you will analyze your data think about the following questions What evidence wil you be looking for in order to identify your unknowns? What relevant chemical equations do you need to consider? · Scientific Argument. Once your group has finished collecting and analyzing your data, you will need to develop an initial argument. Your argument must include a claim. The claim is your answer to the guiding question. Your argument must also include evidence in support of your claim. The evidence is your analysis of the data and your interpretation of what the analysis means. Finally, you must include a justification of the evidence in your argument. The justification needs to use a scientific concept or principle to explain why the evidence that you decided to use is relevant and important. Report. Once you have completed your research, you will need to prepare an investigation report that consists of three sections. Each section should provide an answer for the following questions: 1. What question were you trying to answer and why? 2. What did you do during your investigation and why did you conduct your investigation in this way? 3. What is your argument? our report should answer these questions in 2 pages or less. Be sure to write in a persuasive style, you are trying to convince others that your claim is acceptable or valid!Explanation / Answer
The identities of the unknown chemicals can be determined simply by adding the other three solutions to each of the unknowns and observing the results. This is a sold, false-positive methodology since the possible chemicals among the unkown solutions are known while which unknown is acid, base, indicator or water is only not known. Since each solution will yield a different result upon reacting with the other three by the end of which reactions one can pinpoint the identities of each unknown.
What data will you collect?
Acids on reaction with bases undergo neutralization exothermically which can be observed by the radiation of heat from the test tube. (There will not be appearance of bubble here as it happens only in case of carbonate base neutralization where the bubbles are carbon dioxide).
Phenolphthalein shows no colour in acids as that indicator itself is a weak acid and in acidic medium remains protonated. The protonated form of the indicator is colourless whereas the anionic form is pink. In basic media, the base abstracts the proton of phenolphthalein making the anionic form predominant thus imparting a pink colour to it.
Bases on reaction with acids get neutralized and give a pink colour on reaction with phenolphthalein.
Water does not give any chemical reaction with any of the other solutions. Since the acid solution is also of low concentration, there will be almost no generation of heat when the acidic solution to water or vice versa.
Thus the data to be collected are the colour changes occuring and the production of heat.
How will you collect the data? How will you analyze your data?
If the given solution is water,
water + HCl -----> No heat, no colour change
water + NaOH -----> No heat, no colour change
water + phenolphthalein -----> No heat, no colour change.
Thus the only solution which does not give any data is water.
If the unknown is HCl,
HCl + water -----> Very less heat, no colour change
HCl + NaOH -----> Large amounts of heat, no colour change
HCl + phenolphthalein -----> No heat, no colour change.
Thus HCl is the solution generating heat upon reaction with one unknown but does not give any colour change with any unknown (Colour change is vital as NaOH will also give heat when reacted with HCl but gives pink colour with the indicator)
If the unknown is NaOH,
water + NaOH -----> No heat, no colour change
HCl + NaOH -----> Generation of heat, no colour change
phenolphthalein + NaOH -----> No heat, appearance of pink colour
Thus the unknown giving off heat when reacted with one solution and gives pink colour is NaOH.
If the unknown is phenolphthalein,
phenolphthalein + water -----> No heat, no colour change
phenolphthalein + HCl -----> No heat, no colour change
phenolphthalein + NaOH -----> No heat, appearance of pink colour
Thus the indicator is the solution which does not generate heat with any unknown but gives a pink colour when reacted with one unknown.
In this experiment, irrespective of the unknown solution taken and reacted with others, the observations are exclusive to each chemical and will give the unknown's identity conclusively.