Chemistry Task 3 Video Flashcards
Specifically on the video
Outline what is happening in test tube A.
Addition of HCl –> white precipitate formed. Hydrogen ions will stay in solution (because an acid is a compound that wants to lose/donates a hydrogen as opposed to a base which is a compound that wants to gain a hydrogen)
Describe in a more detailed manner what the result of adding HCl in the test tube A is.
As the hydrogen ions stay in the solution, the white precipitate is insoluble chloride. May either be lead, silver or mercury.
How do we improve the validity of the the test tube A?
A confirmation test must be conducted to assess the specific cation.
Explain what the confirmation test for the test tube A looks like, and how to assess the specific cation.
Filter the precipitate + expose to UV radiation. * If it decomposes into elemental silver, silver was present.
* If not, add potassium iodide, the formation of a yellow precipitate indicates lead, a red precipitate indicates mercury.
What happens in test tube B?
HNO3 is added, bubbles form. Extra HNO3 is added and no bubbles form. Ba(NO3)2 is added, forming a white precipitate. Indicates carbonate ions were present.
How does one improve the validity of test tube B?
S-tube filled with lime water could be corked to the test tube. As the gas formed bubbles through this, a cloudy change indicates the gas formed is carbon dioxide.
What can be inferred about the reaction in test tube B when Ba(NO3)2 is added and forms a white precipitate?
All nitrates are soluble, thus the white precipitate is a barium salt. Specifically barium sulfate. Sulfate ((SO4)2-)ions are present in solution.
What should be noted in reference to Test Tube B?
Barium carbonate, sulfate and phosphate are all white. However: carbonate ions have been eliminated (as bubbles were produced when HNO3 was added) , and barium phosphate only precipitates in an alkali solution.
