Core Practical: Identifying Ions Flashcards
All 6 cards in this deck
Why must the test for any ion be unique?
If more than one ion gave the same result, the test could not identify which ion is present.
True or false? A white precipitate with sodium hydroxide solution identifies the calcium ion.
False.
More than one cation gives a white precipitate (e.g. aluminium, calcium, magnesium, zinc, lead).True or false? Sodium hydroxide solution can be used to test for anions.
False.
Sodium hydroxide solution only tests for cations.Why is dilute acid added before barium chloride solution in the test for sulfate ions?
To remove carbonate ions, which would also give a white precipitate and a false positive.
What safety precaution is needed when using sodium hydroxide solution in ion tests, and why?
Wear eye protection — sodium hydroxide solution is corrosive/an irritant.
What are the steps to identify both ions in an unknown salt?
e.g. a solid gives an orange-red flame, and a white precipitate with dilute nitric acid and silver nitrate solution- Test for the cation (flame test or sodium hydroxide solution): orange-red flame means calcium ions.
- Test for the anion: white precipitate with silver nitrate means chloride ions.
- Name the salt: calcium chloride.