Test for cations Flashcards
What happens when aqueous sodium hydroxide is added to Ammonium?
No ppt. formed, solution remains colourless (same for aqueous ammonia).
On warming, a colourless and pungent gas is evolved.
Gas evolved turns moist red litmus paper blue.
Which four cations form white ppt. when aqueous sodium hydroxide is added?
- Calcium
- Aluminium
- Lead
- Zinc
Which one of the following cations, Calcium, Aluminium, Lead, and Zinc forms white ppt. that is insoluble in excess aqueous sodium hydroxide?
Calcium
Does calcium form ppt. when aqueous ammonia is added?
No ppt. is formed, solution remains colourless.
Which one of the three cations that form white ppt. when aqueous ammonia is added forms white ppt. that is soluble in excess aqueous ammonia to form a colourless solution?
Zinc
What colour ppt. does Copper (II) cation form when both aqueous sodium hydroxide and aqueous ammonia is added?
Light blue ppt.
What colour ppt. does Iron (II) cation and Iron (III) cation form respectively?
Green ppt. and Reddish-brown ppt.
(Both insoluble in excess aqueous sodium hydroxide and aqueous ammonia)
When excess aqueous sodium hydroxide is added to Copper (II) cation, is the light blue ppt. soluble or insoluble?
Light blue ppt. insoluble in excess aqueous sodium hydroxide.
Light blue ppt. turns black on heating
When excess aqueous ammonia is added to Copper (II) cation, is the light blue ppt. soluble or insoluble?
Light blue ppt. soluble in excess aqueous ammonia to give a deep blue solution
What are the three tests to differentiate between Lead and Aluminium cations?
- Add aqueous potassium iodide
- Add dilute sulfuric acid
- Add dilute hydrochloric acid
What are the observations for aqueous potassium iodide test?
(Differentiating between Lead and Aluminium cation)
- Yellow ppt. forms if Lead cation is present.
- No ppt forms, solution remains colourless if Aluminium cation is present.
What are the observations for dilute sulfuric acid test?
(Differentiating between Lead and Aluminium cation)
- White ppt. forms if Lead cation is present.
- No ppt forms, solution remains colourless if Aluminium cation is present.
What are the observations for dilute hydrochloric acid test?
(Differentiating between Lead and Aluminium cation)
- White ppt. forms if Lead cation is present.
- No ppt forms, solution remains colourless if Aluminium cation is present.