Complete the table below using your data from Procedure I. Based on the measured pH determine whether each solution is an acid or a base.
Data Sheet: Activity – Acids and Bases
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Name
Course
Date
BIOL 103
Procedure I – pH of Household Solutions
Complete the table below using your data from Procedure I. Based on the measured pH determine whether each solution is an acid or a base.
Data Table I
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Solution Number
Solution
Solution pH
Acid or Base?
1
Battery Acid
2
Lemon Juice
3
Red Wine
4
Water
5
Antacid
6
Ammonia
7
Oven Cleaner
Procedure II – pH of Biological Solutions
Complete the table below using your data from Procedure II. Based on the measured pH determine whether each solution is an acid or a base.
Data Table II
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Solution Number
Solution
Solution pH
Acid or Base?
1
Urine
2
Liver Bile
3
Skim Milk
4
Tear Fluid
5
Seawater
6
Blood Plasma
7
Stomach Acid
Observations and Questions
[1] Which household solution in Data Table I is the most basic? What information helped you to come to that decision? What can you explain about the chemical composition of the solution based on its pH?
[2] Which biological solution in Data Table II is the most acidic? What information helped you to come to that decision? What can you explain about the chemical composition of the solution based on its pH?
Procedure III – Adding Acid Solution to the Buffer Solution
Complete the table below using your data from Procedure III.
Data Table III
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Number of Added Drops
pH of Non-Buffer Solution
(Water)
pH of Buffer Solution
0
7.00
7.00
1
2
3
4
5
Observations and Questions
[3] What happens to the pH of the water as you add drops of the acid solution (Data Table III)? What is the chemical basis of this change in the pH of the water as acid is added?
[4] Calculate the percent change of pH for water using the formula below.
Percent Change of pH = 100% x ( pH at 5 drops – pH at 0 drops ) / ( pH at 0 drops )
[5] What happens to the pH of the buffer as you add drops of the acid?
[6] Calculate the percent change of pH for the buffer using the formula below.
Percent Change of pH = 100% x ( pH at 5 drops – pH at 0 drops ) / ( pH at 0 drops )
[7] Compare the change in pH for the water solution and the buffer solution as drops of acid are added.
Procedure IV – Adding Base Solution to the Buffer Solution
Complete the table below using your data from Procedure IV.
Data Table IV
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Number of Added Drops
pH of Non-Buffer Solution
(Water)
pH of Buffer Solution
0
7.00
7.00
1
2
3
4
5
Observations and Questions
[8] What happens to the pH of the water as you add drops of the base solution (Data Table IV)? What is the chemical basis of this change in the pH of the water as base is added?
[9] Calculate the percent change of pH for water using the formula below.
Percent Change of pH = 100% x ( pH at 5 drops – pH at 0 drops ) / ( pH at 0 drops )
[10] Calculate the percent change of pH for the buffer using the formula below.
Percent Change of pH = 100% x ( pH at 5 drops – pH at 0 drops ) / ( pH at 0 drops )
[11] The buffer solution is said to “resist” a change in pH. Compare the percentage changes for the water solution and the buffer solution. Do these percentages support a resistance to change for the buffer solution? Explain your answer.
[12] In your own words, explain the chemical basis of how the buffer resists pH changes when the base is added.
[13] Design an experiment testing the impact of different pH levels on plant growth. What would be the levels of your independent variable? Be specific. You would need to vary the pH of a factor that plants need for growth such as soil, fertilizer, or water. What would be your dependent variable; that is, what result would you measure?
Pre-Activity Checklist
· Make sure you know how your computer/device saves screenshots
Follow this link to get details on how to take and save a screenshot
· Read the background material to help you understand the concepts related to this activity
· Get the Activity Form and Additional Data (look under the Activity Form tab)
· Record your Activity Data Code in your Activity Form
· Close any unneeded browser tabs for best performance
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Activity Procedure
In this activity you will explore the pH of two sets of solutions and test the ability of a buffer solution to resist pH changes.
pH Testing
Procedure I ‐ Household Solutions
1. select pH Test by clicking or tapping on its button
2. select Household Solutions by clicking on its button
3. click the Measure pH button
4. record the pH measurements in Data Table I
5. take a screenshot of this completed data run (it will be used to confirm your identity and Activity Data Code)
6. press the reset button and move on to the next procedure
Procedure II ‐ Biological Solutions
1. select pH Test by clicking or tapping on its button
2. select Biological Solutions by clicking on its button
3. click the Measure pH button
4. record the pH measurements in Data Table II
5. press the reset button and move on to the next procedure
Buffer Testing
Procedure III ‐ Adding Acid Solution to the Buffer Solution
In this procedure an acid solution is added drop by drop to water and a buffer solution.
1. select Buffer by clicking or tapping on its button
2. select Acid Solution by clicking on its button
3. click the Add Drop button
4. record the pH of both solutions in Data Table III
5. repeat steps 3-4 four more times (until 5 drops have been added)
6. press the reset button and move on to the next procedure
Procedure IV ‐ Adding Base Solution to the Buffer Solution
In this procedure a base solution is added drop by drop to water and a buffer solution.
1. select Buffer by clicking or tapping on its button
2. select Base Solution by clicking on its button
3. click the Add Drop button
4. record the pH of both solutions in Data Table IV
5. repeat steps 3-4 four more times (until 5 drops have been added)
6. press the reset button and move on to the Post-Activity
Post-Activity
Complete Table I, Table II, and all questions on your Activity Form. To help with the questions, please review the background material and your data.
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Section 2
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