Concise Study Guide for OCR A Level Chemistry

Qualitative Analysis of Ions

• Positive Ions:

• Dissolve solid in deionised water.

• Test Group 2 metal ions:

  • Use barium chloride and sodium hydroxide.
  • Record precipitates (yellow, white).

• Test ammonium ions (NH4+):

  • Add sodium hydroxide in water bath.
  • Ammonia detected by litmus paper.

• Negative Ions:

• Test halide ions with nitric acid + silver nitrate.

  • Precipitate colors: white (Cl-), cream (Br-), yellow (I-).

• Test carbonate ions (CO3 2-):

  • Add dilute hydrochloric acid (effervescence indicates CO2).

• Test sulfate ions (SO4 2-):

  • Precipitate of barium sulfate forms in presence.

Synthesis of a Haloalkane:

• Haloalkane synthesized from alcohol in fume hood with hydrochloric acid.
• Separate layers and dry with magnesium sulfate.
• Distillation at 47-53°C to collect product.

Preparation of Cyclohexene:

• Dehydration of cyclohexanol using phosphoric acid.
• Purification involves washing with sodium hydrogen carbonate and drying with calcium chloride.
• Perform a bromine test for unsaturation (orange to colorless).

Oxidation of Ethanol:

• Primary alcohol oxidizes to aldehyde, further to carboxylic acid.
• Uses acidified potassium dichromate.

Hydration of Hex-1-ene:

• Hex-1-ene + concentrated sulfuric acid reacts to form hexan-2-ol.
• Separating and drying the product before distillation.

Testing for Functional Groups:

• 2,4-Dinitrophenylhydrazine tests for carbonyl groups.
• Tollens' reagent tests for aldehydes (silver mirror = positive).
• Bromine water used for unsaturation detection (alkenes).

Bonding & Structure:

• Ionic bonds: transfer of electrons from metals to non-metals.
• Covalent bonds: sharing electrons between two non-metals.

Transition Elements:

• Form colored compounds and have variable oxidation states.
• Complex ions formed from ligands attaching to metal ions.
• Ligand substitution can change coordination number and geometry.