Acids and Bases Lab

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Acids and Bases Lab

Mr. Filipek, early bird

Purpose:
The purpose of this lab is to test the buffer range of different substances. What this mean is that different substances will be tested to see which one have high resistance in pH level. In the lab, the independent variable will be the number of drop of acids or base put into the substance. The dependence variable is the pH of a substance. Water will be the control group in the experiment and the other substance will compare their pH level to water.
Introduction:
Acids and bases are classified through numerical value on a pH. A pH scale measures the hydrogen ion concentration in a solution. Anything ranging from a 1 on the scale to a 6 is considered to be an acid whereas anything from an 8 to a 14 is basic. A 7 represents neutrality and an even concentration of hydrogen ions in a solution. More specifically, an acid is a substance with more [H+] than [OH-] and vice versa with a base where it has more [OH-] than [H+]. pH declines as [H+] rises, which explains how acidic solutions, such as a solution with a pH of 2, have a higher [H+] concentration. There are substances that are used to resist pH change. Buffers are substances that minimize changes in [OH-] and [H+] concentrations.
Methods:
We started by labeling one beaker acid and one basic because we wanted to measure how certain solutions react to change when introduced to a more acidic or basic liquid. We then used the awesome new Lab Quest probes to be able to measure the change the solution went through. Our group used the buffered aspirin solution to measure the change. Slowly, we added 5 drops of acid (HCL) to one beaker and base (NaOH) to the other. Thankfully the Lab Quest graphed and charted everything for us, but it allowed us to see the change of the solution becoming more basic or acidic. We did this five more times to get a wider range of data.

Data:

Graphs and Charts:

Discussion:
Basis of the Experiment:
We did the lab to measure the acidity and the base of water. We first started by using two 50 ml beakers of water. We then labeled one beaker acid and the other base. After labeling we took the probes and rinsed them with distilled water. After cleaning we took the probes and measured the acidity and base of water. After taking the initial measurement we started to add 5 drops of acid to beaker labeled acid and 5 drops of base to the beaker labeled base.
Results of the Experiment:

o   Initial measure of water: PH  = 6.33 for the acid beaker and PH = 9.02 for the base beaker

o   After 5 drops of acid resulted in PH  = 5.71 for the acid beaker and PH = 8.98 for the base beaker

o   After 10 drops of acid resulted in PH  = 5.07 for the acid beaker and PH = 8.96 for the base beaker

o   After 15 drops of acid resulted in PH  = 4.59 for the acid beaker and PH = 9.22 for the base beaker

o   After 20 drops of acid resulted in PH  = 4.29 for the acid beaker and PH = 10.05 for the base beaker

o   After 25 drops of acid resulted in PH  = 4.09 for the acid beaker and PH = 10.44 for the base beaker

o   After 30 drops of acid resulted in PH  = 3.88 for the acid beaker and PH = 10.55 for the base beaker

Summary:

-      The results of the measurements from the base beaker were inconsistent, since the pH level dropped for the first couple of measurements and then it started to increase again.

-      The results of the measurements from the acid beaker were linear with the addition of acid drops throughout the experiment.

-      The measurements from the base beaker should have been linear just like the acid beaker. This might have been due to dirty base beaker or probe.

-      Lastly the outcome from the experiment was as predicted. The results from the acid beaker showed that the pH level went down with every addition of acid. The base beaker results became consistent after the third addition of acid.

 Conclusion:

In our experiment, we first had to test how acids and bases reacted with water. We did this so we could have a reference point during our later experiments. Since water was neutral, it started with a pH of around 7. Each time we recorded data, we added 5 drops of acid and base. We noticed that every time we added acid drops, the pH went down consistently until it reached a pH of about 2.5. The same thing occurred when we added base, only to increase pH until it reached about 11.5. This showed that the way didn't resist much to the change in pH. After that, we decided to test the same thing but with dissolved aspirin. The same results followed; a decrease in pH when acid was added and an increase in pH when base was added. However, we saw that aspirin resisted change more than water, for the change in pH as we added drops was not as significant.

References:
We did not use any references.