Chem Topic 7

In a hydrogen bond, what atoms could be bonded to the hydrogen

• Nitrogen

• Oxygen

What is the trend in boiling temperatures of hydrogen halides up to Hydrogen iodide

HF has the highest, HCl the lowest, then they increase in BT

What is a disproportionation reaction

A reaction where an element in the same species is simultaneously reduced and oxidised

Oxidation number rules for flourine

Always -1

Oxidation number rules for hydrogen

Always +1 unless combined with a less electronegative element, where it becomes -1

Oxidation number rules for oxygen

-2 unless:

• Combined with flourine which makes it +2

• In a peroxide which makes it 1-

solubility of group 2 compounds

• Nitrates: soluble

• Chlorides: soluble

• Hydroxides: increase solubility down the group

• Sulfates: decrease solubility down the group

How does the CO₂ test work chemically

Calcium hydroxide (lime water) reacts with CO₂ to form calcium carbonate (insoluble) so the white precipitate turns the solution cloudy.

Test for sulfate ions

Dilute acid like nitric acid + barium nitrate

How can greater thermal decomposition of nitrate be distinguished by minor decomposition

Greater decomposition released brown fumes from the NO₂

Thermal stability trends of group 1 & 2 nitrates

The stability increases down the groups, and group 2 is less stable (higher charge density → lower stability)

Formula for decomposition of metal nitrates

Metal nitrate → Metal nitrite + Oxygen

Metal nitrate → Metale oxide + Nitrogen dioxide + oxygen

Formula for decomposition of metal carbonates

Metal carbonate → Metal oxide + Carbon dioxide

Test for ammonium ions

Sodium hydroxide solution and damp red litmus

What is produced when hydrogen halides react with water

A colourless acid