Data Sheet: Activity – Acids and Bases

Data Sheet: Activity – Acids and Bases

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Name Course Date

Activity Data Code LCG

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

Solution Number Solution Solution pH Acid or Base?
1 Battery Acid 0.0 Acid
2 Lemon Juice 2.00 Acid
3 Red Wine 3.80 Acid
4 Water 7.00 Neutral
5 Antacid 10.00 Base
6 Ammonia 12.00 Base
7 Oven Cleaner 14.00 Base

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

Solution Number Solution Solution pH Acid or Base?
1 Urine 5.25 Acid
2 Liver Bile 8.60 Base
3 Skim Milk 6.60 Acid
4 Tear Fluid 7.00 Neutral
5 Seawater 8.00 Base
6 Blood Plasma 7.40 Base
7 Stomach Acid 2.50 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

Number of Added Drops pH of Non-Buffer Solution
(Water) pH of Buffer Solution
0 7.00 7.00
1 2.30 6.97
2 2.00 6.94
3 1.82 6.91
4 1.70 6.87
5 1.60 6.84

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

Number of Added Drops pH of Non-Buffer Solution
(Water) pH of Buffer Solution
0 7.00 7.00
1 11.70 7.03
2 12.00 7.06
3 12.18 7.09
4 12.30 7.12
5 12.40 7.15

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?