Chapter 16.2, pp 506 - 510
Do
Problems 13, 15, 16
Lab prep for Tuesday:
Please read instructions for this lab, as time is limited, and we won't have enough time if you don't prepare.
pH Lab
Test-tubes with a capacity of around 10 mL are ideal. The test-tubes should be as clean as possible. Test-tubes, dropping pipettes and measuring cylinders should be washed in tap water and then rinsed with deionised or distilled water.
Procedure
Students 1 and 2
Test-tubes with a capacity of around 10 mL are ideal. The test-tubes should be as clean as possible. Test-tubes, dropping pipettes and measuring cylinders should be washed in tap water and then rinsed with deionised or distilled water.
Procedure
Students 1 and 2
a Number the test-tubes 1–7.
b Half-fill test-tube 1 with the hydrochloric acid solution.
c Transfer 1 mL of the hydrochloric acid into the measuring cylinder. Add distilled or deionised water to the measuring cylinder, up to the 10 mL mark.
d Pour some of the resulting diluted solution from the measuring cylinder into test-tube 2, enough to come to a similar height as the solution in test-tube 1.
e Carefully, pour away all but 1 mL of the solution remaining in the measuring cylinder. Now add distilled or deionised water to the measuring cylinder up to the 10 mL mark. Pour the resulting solution into test-tube 3. Continue in this way until you have solutions in test-tubes 1 to 6. Put only distilled or deionised water into test-tube 7.
Students 3 and 4
f Repeat instructions a – e using the sodium hydroxide solution instead of hydrochloric acid. Number the test-tubes 8–13.
Both groups
g Put the two racks of test-tubes together so that the solutions are in order 1 to 13. The test-tubes now have solutions in them with pH 1 (test-tube 1) to pH 13 (test-tube 13).
h Add a drop of Universal indicator to each test-tube. Rock each test-tube from side to side to mix the contents. Add more Universal indicator solution to each test-tube if needed to allow the colours to be seen more clearly. Be sure to add the same number of drops of indicator to each test-tube.
i Compare the colors of the solutions with the pH indicator chart.
b Half-fill test-tube 1 with the hydrochloric acid solution.
c Transfer 1 mL of the hydrochloric acid into the measuring cylinder. Add distilled or deionised water to the measuring cylinder, up to the 10 mL mark.
d Pour some of the resulting diluted solution from the measuring cylinder into test-tube 2, enough to come to a similar height as the solution in test-tube 1.
e Carefully, pour away all but 1 mL of the solution remaining in the measuring cylinder. Now add distilled or deionised water to the measuring cylinder up to the 10 mL mark. Pour the resulting solution into test-tube 3. Continue in this way until you have solutions in test-tubes 1 to 6. Put only distilled or deionised water into test-tube 7.
Students 3 and 4
f Repeat instructions a – e using the sodium hydroxide solution instead of hydrochloric acid. Number the test-tubes 8–13.
Both groups
g Put the two racks of test-tubes together so that the solutions are in order 1 to 13. The test-tubes now have solutions in them with pH 1 (test-tube 1) to pH 13 (test-tube 13).
h Add a drop of Universal indicator to each test-tube. Rock each test-tube from side to side to mix the contents. Add more Universal indicator solution to each test-tube if needed to allow the colours to be seen more clearly. Be sure to add the same number of drops of indicator to each test-tube.
i Compare the colors of the solutions with the pH indicator chart.
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