Planning and Design Chemistry Lab – Plan and Design an experiment that can be used to determine the contents of four bottles found in your home

Planning and Design Chemistry Lab – Plan and Design an experiment that can be used to determine the contents of four bottles found in your home

Problem:

You venture in a cellar one day and found four stoppered bottles. The labels were found on the floor next to the bottles and were marked: dilute sulphuric acid, sodium carbonate, calcium hydroxide and distilled water. If you were handed a pack of blue litmus paper and a rack of test tube, plan and design an experiment that can be used to determine the contents of each bottle. Label the bottles A, B, C and D before you begin your investigation.

Hypothesis:

Bottle A contains Sodium carbonate (Na2CO3), Bottle B contains (H2O), Bottle C contains Sulphuric acid (H2SO4) and Bottle D contains Ca(OH)2.

Aim:

To determine if the contents in Bottle A is Na2CO3, Bottle B is H2O, Bottle C is H2SO4 and Bottle D is Ca(OH)2 using litmus paper

Apparatus / Materials:

blue litmus paper, test-tube, test-tube rack and solutions in bottle

Method:

  1. Label the test-tube A-D
  2. Pour out 5cm of each solution in its corresponding test-tube.
  3. Place a blue litmus paper in each test-tube and observe for a color change to red
  4. The solution that changed the litmus paper to red would be the H2SO4, which is the acid.
  5. Label the corresponding solution as H2SO4.
  6. The test-tubes that were not identified will now be tested.
  7. Use the H2SO4 to change 3 litmus papers to red.
  8. Place the now red litmus papers in the remaining solutions. Observe for a color change to blue. Two of your solution will change to blue. The one that does not change is the water
  9. Label the corresponding bottle as H2O, and set it aside.
  10. The remaining two (2) solutions are the calcium hydroxide and the sodium carbonate.
  11. Add 2 cm of the H2SO4 to the 2 unknown test-tube and note your observations.
  12. The test-tube that showed signs of bubbling/effervescence would be the carbonate, Na2CO3.
  13. Label the corresponding bottle as Na2CO3 and the final bottle as hydroxide.

Expected Results:

Chemistry diagram 3

This test showed that one of the solutions turned the blue litmus paper red. This was identified as the sulphuric acid (H2SO4).

Chemistry diagram 4

 

This test would show two solutions changing the litmus paper to blue, the one that was not changed would be the water. Use the acid to test the remaining two unknowns to differentiate between them.

Chemistry diagram 5

Variables

 

  • Manipulated- Test carried out on the solutions
  • Controlled- Amount of solutions used
  • Responding- reaction with the litmus paper and the acid

 

Treatment of results

 

Label the bottles corresponding to the observations made when each was tested with litmus paper and the sulphuric acid.

 

Interpretation of results

 

If the contents in Bottle A reacted with sulphuric acid then it should be the sodium carbonate, if the contents of Bottle B did not change the color of the red litmus paper then it was the water. If the contents of Bottle C changed the blue litmus paper to red then it would be the acid and if the contents of Bottle D did not react with the acid then it would be the hydroxide.

 

The data collected would then support the hypothesis. If the contents of each of the bottles reacted differently with the blue litmus paper then the data collected does not support your hypothesis.

 

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