1.1 - Flame Tests

Materials and Apparatus Required

Chemicals

• Lithium chloride
• Sodium chloride
• Potassium chloride
• Barium chloride
• Strontium chloride
• Copper(II) chloride
• Concentrated hydrochloric acid

Apparatus

• Platinum or nichrome wire held in a glass rod (or wooden splints)
• Bunsen burner
• Six small beakers
• Test tubes
• Pestle and mortar

Safety Precautions

• Wear safety glasses at all times.
• Handle concentrated hydrochloric acid with care; it is highly corrosive and can irritate the lungs.
• Copper(II) chloride is toxic if swallowed and can irritate the eyes and skin.
• Barium chloride and lithium chloride are harmful by ingestion or inhalation.
• Ensure proper disposal by diluting with excess water and neutralizing with sodium carbonate.

Method

Using Platinum/Nichrome Wire:

1. Clean the wire by dipping it in concentrated hydrochloric acid.
2. Heat the wire in the Bunsen burner flame until no colour is emitted (indicating it is clean).
3. Crush a small amount of the salt with a pestle and mortar.
4. Dip the clean wire into hydrochloric acid, then into the salt.
5. Hold the wire in the flame and observe the colour.
6. Record the colour of each metal.
7. If testing multiple salts, use separate wires or clean thoroughly between tests to avoid contamination.

Using Wooden Splints:

1. Soak wooden splints in water overnight.
2. Crush a small amount of salt with a pestle and mortar.
3. Dip a soaked splint into the salt.
4. Wave the splint gently in the flame and note the colour.
5. Use a fresh splint for each salt to avoid contamination.

Results

• Lithium: Deep red flame
• Sodium: Yellow flame
• Potassium: Lilac flame
• Barium: Yellow-green flame
• Strontium: Red flame
• Copper: Blue-green flame

Example Questions with Answers