Chemical Tests

• How do you test for hydrogen gas?

  Place a burning splint near the gas; a "pop" sound confirms the presence of hydrogen.
• How do you test for oxygen gas?

  Insert a glowing splint into the gas; if it relights, oxygen is present.
• How do you test for carbon dioxide gas?

  Bubble the gas through limewater (calcium hydroxide solution); it turns milky/cloudy if CO₂ is present.
• How do you test for chlorine gas?

  Hold damp blue litmus paper near the gas; it turns red, then bleaches white.
• How do you test for ammonia gas?

  Hold damp red litmus paper near the gas; it turns blue.
• What color does lithium (Li⁺) burn in a flame test?

  Red flame
• What color does sodium (Na⁺) burn in a flame test?

  Yellow/orange flame
• What color does potassium (K⁺) burn in a flame test?

  Lilac flame
• What color does calcium (Ca²⁺) burn in a flame test?

  Brick-red flame
• What color does copper (Cu²⁺) burn in a flame test?

  Blue-green flame
• What is the result of adding NaOH to copper (Cu²⁺)?

  A blue precipitate (Cu(OH)₂) forms.
• What is the result of adding NaOH to iron(II) (Fe²⁺)?

  A green precipitate (Fe(OH)₂) forms.
• What is the result of adding NaOH to iron(III) (Fe³⁺)?

  A brown precipitate (Fe(OH)₃) forms.
• What is the result of adding NaOH to ammonium (NH₄⁺) and heating?

  Ammonia gas is released, turning damp red litmus paper blue.
• How do you test for carbonate ions (CO₃²⁻)?

  Add dilute acid (e.g., HCl). Fizzing occurs, and CO₂ gas is released (test with limewater).
• How do you test for sulfate ions (SO₄²⁻)?

  Add HCl (to remove impurities) and barium chloride (BaCl₂); a white precipitate forms.
• How do you test for chloride ions (Cl⁻)?

  Add dilute nitric acid (HNO₃) and silver nitrate (AgNO₃); a white precipitate of AgCl forms.
• How do you test for bromide ions (Br⁻)?

  Add dilute nitric acid (HNO₃) and silver nitrate (AgNO₃); a cream precipitate of AgBr forms.
• How do you test for iodide ions (I⁻)?

  Add dilute nitric acid (HNO₃) and silver nitrate (AgNO₃); a yellow precipitate of AgI forms.
• How do you test for the presence of water using anhydrous copper(II) sulfate?

  Add water to anhydrous copper sulfate; it turns from white to blue.
• How do you test if a sample is pure water?

  Measure the boiling point; pure water boils at 100°C and freezes at 0°C.