RP4- Identifying Cations And Anions Flashcards
Describe a method for identifying group 2 ions
- place ten drops of 0.1 moldm3 of a group 2 chloride into a clean test tube
- add ten drops of 0.6 moldm3 of NaOH. Record any observations
- continue to add until NaOH is in excess. Record any observations
- dispose of the products by placing the test tube in a bowl of water.
- repeat with other group 2 chlorides
When testing for group 2 ions with NaOH, what are the observations with magnesium, calcium, strontium and barium chloride in NaOH and excess NaOH?
ALL INITIALLY COLOURLESS SOLUTIONS
Mg- slight white ppt in 10 drops, white ppt in excess
Ca- slight white ppt in 10 drops, slight white ppt in excess
St- slight white ppt in 10 drops, slight white ppt in excess
Ba- colourless solution in 10 drops, colourless solution in excess (no observable changes)
Describe a method to test for group 2 ions with dilute sulfuric acid
Add 10 drops of 0.1 moldm3 group 2 chlorides to a clean test tube
Add 10 drops of dilute sulfuric acid, mix well and record any observations
Continue t add the sulfuric acid, a drop at a time whilst continuously stirring until in excess. Record any new observations
Repeat with other group two chlorides
What observations will be seen when group 2 chlorides are reacted with dilute H2SO4, and excess H2SO4?
Mg- slight white ppt in 10 drops, colourless in excess
Ca- slight white ppt in 10 drops, slight white ppt in excess
St- white ppt in 10 drops, white ppt in excess
Ba- white ppt in 10 drops, white ppt in excess
Describe a method to test for ammonium ions
Add 10 drops of ammonium chloride to a clean test tube, add 10 drops of NaOH and shake to mix contents well
Warm the mixture in the test tube using a water bath
Use FORCEPS to hold a piece of damp red litmus paper at the mouth of the test tube, the litmus paper will turn blue if ammonium ions are present because they are basic
Dispose of the contents in boiling water
How does damp red litmus paper react in both acids and bases?
Remains red in acids, and turns blue in bases
Describe a method to test for carbonate ions
Add equal volumes of sodium carbonate and dilute HCl in a test tube
Use a delivery tube to transfer the gas produced into a second test tube with limewater (calcium hydroxide solution) and a bung to stopper
If carbonate ions were present carbon dioxide will form a white ppt in the limewater (calcium carbonate produced is a white solid)
Describe a method to test for sulfate ions
Add equal volumes of dilute HCl and barium chloride to the solution (HCl ensures other compounds that can effect the reaction are removed)
A white ppt of barium sulfate will be formed
Add a small volume of HCl, if the ppt does not dissolve, sulfate ions are present
