Testing pH Lab



Testing pH Lab

Purpose- To determine the pH of some common solutions and samples of water

Materials

- stir rod - test tubes & test tube rack - universal indicator

- tweezers - 10 mL graduated cylinder - pH paper and chart

Procedure

1) Label your test tubes A-H with wax pencil or tape.

2) Pour 10 mL of your solutions into test tubes A-D. Label Table 1 with the type of solution in each test tube.

3) Pour 5 mL of the provided solutions into test tubes E-H. Label Table 1 with the type of solution in each test tube.

4) Hypothesize about the pH of each of the solutions. Use your previous knowledge of the solutions and knowledge of pH to create your hypothesis. Record your hypothesis in Table 1. (You will have to create a table with the appropriate number of rows. Use the column headings shown in Table 1 below)

Table 1

|Solutions |Hypothesis of pH |Litmus Paper |Universal Indicator |pH meter |

|A | | | | | |

|B | | | | | |

5) Obtain a piece of litmus paper for each solution you will test. Use tweezer to dip the tip of litmus strip into the test tubes. If the red paper turns blue, and the blue paper stays blue the solution is basic. If the blue paper turns red, and the red paper stays red the solution is acidic.

6) Once the pH paper has been recorded, obtain the universal indicator. Add 6 drops of indicator into A-D. Add 3 drops indicator into E-H. Use the stir rod to mix the indicator in being sure to clean the stir rod between each solution with DI water.

7) Use the pH chart to determine the indicator pH. If color does not match any color on the package, estimate the pH. Record the pH in table 1 for each solution.

8) Finally, use the pH probe. Pour some solution into the 100 mL beaker. Clean the probe with DI water into the waste beaker. Place the probe into the solution, take your measurement and record in table 1. Rinse the pH probe and wash out your beaker for the next solution.

Discussion

1) Arrange your solution in order from most acidic to least acidic. Place the names of the solutions on the pH scale according to your results.

2) Was the pH of any of the solutions significantly different than what you hypothesized? Explain

3) What is the pH range of the solutions you tested? What solution was the most acidic and the most basic?

Complete the following chart by:

4) Calculate the pOH for each solution

5) Calculate the [H+] for each solution

|Solution |pH |pOH |[H+] |

|A | | | |

|B | | | |

6) What pattern do you see between pH and pOH?

7) What pattern do you see between pH and [H+]?

8) Do you notice anything about the solutions on the pH scale, their pH, and their location on the pH scale?

Testing pH Lab Pre-AP

Purpose- To determine the pH of some common solutions and samples of water

Materials

- stir rod - test tubes & test tube rack - universal indicator

- tweezers - 10 mL graduated cylinder - pH paper and chart

Procedure

1) Label your test tubes A-H with wax pencil.

2) Pour 10 mL of your water solutions into test tubes A-D. Add 5 mL of household item to test tube E-H. Add 5 mL of water to test tubes E-H. Label Table 1 with the type of solution in each test tube.

4) Hypothesize about the pH of each of the solutions. Use your previous knowledge of the solutions and knowledge of pH to create your hypothesis. Record your hypothesis in Table 1. (You will have to create a table with the appropriate number of rows. Use the column headings shown in Table 1 below)

Table 1

|Solutions |Hypothesis of pH |pH paper |Universal Indicator |

|A | | | | |

|B | | | | |

5) Obtain a piece of pH paper for each solution you will test. Use tweezer to dip the tip of pH strip into the test tubes. Place pH strip onto a white surface (scratch paper).

6) Use the pH chart to determine the indicator pH. If color does not match any color on the package, estimate the pH. Record the pH in table 1 for each solution.

6) Once the pH paper has been recorded, obtain the universal indicator. Add 6 drops of indicator into A-H. Use the stir rod to mix the indicator in being sure to clean the stir rod between each solution with DI water.

7) Use the pH chart to determine the indicator pH. If color does not match any color on the package, estimate the pH. Record the pH in table 1 for each solution.

8) Pour the solutions down the drain when done and run the water for 1 minute. Wash all test tubes and place upside down in the rack. Clean up your lab area.

Discussion

1) Arrange your solution in order from most acidic to least acidic. Place the names of the solutions on the pH scale according to your results.

2) Was the pH of any of the solutions significantly different than what you hypothesized? Explain

3) What is the pH range of the solutions you tested? What solution was the most acidic and the most basic?

Complete the following chart by:

4) Calculate the pOH for each solution

5) Calculate the [H+] for each solution

|Solution |pH |pOH |[H+] |

|A | | | |

|B | | | |

6) What pattern do you see between pH and pOH?

7) What pattern do you see between pH and [H+]?

8) Do you notice anything about the solutions on the pH scale, their pH, and their location on the pH scale?

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