Identification of Anions

These flashcards cover the identification methods and observations related to various anions using dilute and concentrated acids, as well as barium ions.

What can carbonate ions and sulphite ions be identified by when adding dilute acid to a sample?

Effervescence and gas evolved.

What observation indicates the presence of carbonate ions when adding dilute acid?

Effervescence and gas that turns lime water milky.

What is the equation for the reaction of carbonate ions with dilute acid?

CO3^(2-)(s) + 2H^(+)(aq) -> H2O(l) + CO2(g).

What gas is produced when sulphite ions react with dilute acid?

SO2 gas which decolourises KMnO4 or changes KCr2O7 from orange to green.

What anions can be identified by adding concentrated sulphuric acid?

Carbonate, sulphite, chloride, bromide, and iodide ions.

What is the observation for chloride ions when adding concentrated sulphuric acid?

Gas evolved (HCl) which forms dense white fumes when in contact with glass rod dipped in concentrated ammonia.

What reaction occurs when bromide ions are treated with concentrated sulphuric acid?

Orange-brown vapours (Br2) are evolved.

What is formed when iodide ions are heated with concentrated sulphuric acid?

Purple-black solid that sublimes to a purple vapour.

How are anions identified using barium ions and dilute acid?

By making a solution of the solid, adding barium nitrate or barium chloride, followed by dilute acid.

What observation indicates the presence of sulphate ions when adding barium nitrate/chloride?

White precipitate (ppt) formed.

What happens when carbonate ions react with barium ions in dilute acid?

White precipitate dissolves and CO2 gas is evolved, turning lime water milky.