Pure Chemistry Archives - Page 3 of 14 - Study notes, tips, worksheets, exam papers

Silicon dioxide has a giant molecular structure, consisting of a large number of silicon and oxygen atoms covalently bonded to form a big tetrahedral structure. A lot of energy is needed to break the strong covalent bonds, resulting in the high melting point and boiling point of silicon dioxide.

Describe the test for nitrate ions.

8984 admin

10/11/2023 at 11:50 am (last edited 10/11/2023 at 11:50 am)

Add aqueous sodium hydroxide and aluminium foil into a sample of the solution, and warm gently. If a pungent colorless gas is produced, which turns damp red litmus blue, it shows the presence of nitrate ions.

Describe the test for hydrogen gas.

8982 admin

10/11/2023 at 11:44 am (last edited 10/11/2023 at 11:44 am)

Insert a lighted splint into a test tube of the gas. If the lighted splint is extinguished with a ‘pop’ sound, it shows the presence of hydrogen gas.

Describe the test for Cu2+ ions using aqueous sodium hydroxide.

8979 admin

10/11/2023 at 11:33 am (last edited 10/11/2023 at 11:33 am)

Add a few drops of aqueous sodium hydroxide into a sample of the solution, followed by adding aqueous sodium hydroxide in excess. If a blue precipitate forms which is insoluble in excess of aqueous sodium hydroxide, it shows the presence of Cu2+ ions.