Tests for Anions, Cations and Gases

Front

Anion

Back

A negative ion

Answer explanation

An anion is defined as a negatively charged ion, which means it has gained one or more electrons. This distinguishes it from a positive ion, known as a cation. Therefore, the correct answer is 'a negative ion'.

Front

What is a cation?

Back

a positive ion

Answer explanation

A cation is defined as a positively charged ion, which means it has lost one or more electrons. This distinguishes it from an anion, which is a negatively charged ion. Therefore, the correct answer is 'a positive ion'.

Front

What is the test for a carbonate ion (CO₃^2-)?

Back

add an acid - effervescence and CO₂ is produced

Answer explanation

The test for carbonate ions (CO3^2-) involves adding an acid, which produces effervescence due to the release of CO2 gas. This is a characteristic reaction that confirms the presence of carbonate ions.

Front

What is the test for a Chloride ion (Cl^-)?

Back

acidify with nitric acid and add silver nitrate - white ppt is formed

Answer explanation

The correct test for chloride ions involves acidifying the solution with nitric acid and then adding silver nitrate, which results in the formation of a white precipitate of silver chloride (AgCl).

Front

Test for a Nitrate ion (NO₃^-)?

Back

add NaOH and then aluminium foil - ammonia is produced

Answer explanation

The correct test for nitrate ions (NO3-) involves adding NaOH and then aluminum foil, which reduces the nitrate to ammonia, producing a distinct smell. This confirms the presence of nitrate ions.

Front

Test for a Sulphate ion (SO₄^2-)?

Back

acidify and add barium nitrate - White ppt is formed

Answer explanation

The test for a Sulphate ion (SO4^2-) involves acidifying the solution and adding barium nitrate, which results in the formation of a white precipitate of barium sulphate (BaSO4). This confirms the presence of sulphate ions.

Front

What is a precipitate?

Back

An insoluble solid formed in a reaction

Answer explanation

A precipitate is defined as an insoluble solid that forms during a chemical reaction. This distinguishes it from soluble substances, making "An insoluble solid formed in a reaction" the correct choice.

Front

What is the positive test result when ammonia (NH₄⁺) is added to NaOH?

Back

ammonia is produced on warming

Answer explanation

When NH4+ is added to NaOH and warmed, ammonia (NH3) is released as a gas. This is a characteristic reaction of ammonium ions with strong bases, confirming that ammonia is produced on warming.

Front

What is the positive test result when a calcium ion (Ca²⁺) is added to NaOH or aqueous ammonia?

Back

White ppt is formed

Answer explanation

When calcium ions (Ca²⁺) are added to NaOH, a white precipitate of calcium hydroxide (Ca(OH)₂) is formed. This indicates a positive test result, confirming the presence of calcium ions.

Front

What is the positive test result when a copper ion (Cu²⁺) is added to NaOH or aqueous ammonia?

Back

Light blue ppt is formed (forms a dark blue solution)

Answer explanation

When Cu²⁺ is added to NaOH or aqueous ammonia, a light blue precipitate is formed, which can dissolve to give a dark blue solution upon warming, confirming the presence of copper ions.