Chemical Tests Flashcards
Test for Alkenes (C=C)?
Reagent. Bromine water (Br₂(aq))
Positive result: decolorization from orange to colorless.
What indicates a positive result when testing Haloalkanes (R-X) with silver nitrate solution?
- Chloroalkane: White precipitate (AgCl, dissolves in dilute NH₃)
- Bromoalkane: Cream precipitate (AgBr, dissolves in concentrated NH₃)
- Iodoalkane: Yellow precipitate (AgI, insoluble in NH₃)
The test is conducted by warming with silver nitrate solution (AgNO₃) in ethanol.
Test for Alcohols (R-OH)?
Reagent: Acidified potassium dichromate (K₂Cr₂O₇ + H₂SO₄)
Positive result: primary and secondary alcohols is indicated by a color change from orange to green.
What is the result of the Fehling’s Test for Aldehydes (R-CHO)?
Blue to brick-red precipitate
This test involves heating with Fehling’s solution.
What indicates a positive result for Aldehydes using Tollens’ Test?
Silver mirror forms
This test also involves heating with Tollens’ reagent.
What is the outcome when testing for Ketones (R-CO-R) with Fehling’s or Tollens’ reagent?
No visible change
Ketones do not react with these reagents.
What reagent is used to test for Carboxylic Acids (R-COOH)?
Sodium carbonate (Na₂CO₃)
Positive result is indicated by effervescence due to CO₂ gas produced.
What is indicated by a purple solution in the FeCl₃ Test for Phenol (Ar-OH)?
Positive result
This test involves adding iron(III) chloride.
What happens when Phenol is tested with sodium hydroxide (NaOH)?
Dissolves, forming a colorless solution
This test indicates the solubility of phenol in NaOH.
What is the result of testing Phenol with sodium carbonate (Na₂CO₃)?
No effervescence
This indicates that phenol does not react with sodium carbonate.
Fill in the blank: A positive result for primary and secondary alcohols in the acidified potassium dichromate test shows a change from orange to _______.
green
This indicates oxidation of the alcohols.
What is the reagent used to test for Carbonate (CO₃²⁻)?
Dilute acid (HCl/H₂SO₄)
This test identifies the presence of carbonate ions through effervescence.
What indicates a positive result for the Carbonate test?
Effervescence (CO₂ gas, turns limewater milky)
The formation of CO₂ gas leads to the milky appearance in limewater.
What is the reagent used to test for Sulfate (SO₄²⁻)?
Barium chloride (BaCl₂) with HCl
This test is used to detect sulfate ions by forming a precipitate.
What indicates a positive result for the Sulfate test?
White precipitate (BaSO₄)
The formation of barium sulfate confirms the presence of sulfate ions.
What is the reagent used to test for Ammonium (NH₄⁺)?
Sodium hydroxide (NaOH) and warm
Heating with NaOH helps release ammonia gas for detection.
What indicates a positive result for the Ammonium test?
Ammonia gas released (turns damp red litmus paper blue)
The change in litmus paper color confirms the presence of ammonia.
What is the reagent used to test for Halide Ions (Cl⁻, Br⁻, I⁻)?
Silver nitrate (AgNO₃) and dilute nitric acid (HNO₃)
This test differentiates between various halide ions based on precipitate color.
What indicates a positive result for Chloride (Cl⁻) in the Halide test?
White precipitate (AgCl, dissolves in dilute NH₃)
Chloride ions form a white precipitate that is soluble in dilute ammonia.
What indicates a positive result for Bromide (Br⁻) in the Halide test?
Cream precipitate (AgBr, dissolves in concentrated NH₃)
Bromide ions create a cream-colored precipitate that dissolves in concentrated ammonia.
What indicates a positive result for Iodide (I⁻) in the Halide test?
Yellow precipitate (AgI, insoluble in NH₃)
Iodide ions yield a yellow precipitate that does not dissolve in ammonia.
What is the reagent used to test for Nitrate (NO₃⁻)?
Sodium hydroxide (NaOH) and Devarda’s alloy, then warm
This method helps to release ammonia gas, indicating the presence of nitrate.
What indicates a positive result for the Nitrate test?
Ammonia gas released (turns damp red litmus paper blue)
Similar to the ammonium test, the change in litmus paper color confirms nitrate presence.
Test for Hydrogen (H₂)
Apply a lit splint
Positive result: Squeaky pop
Test for Oxygen (O₂)
Insert a glowing splint
Positive result: Splint relights
Test for Carbon Dioxide (CO₂)
Bubble through limewater (Ca(OH)₂)
Positive result: Limewater turns cloudy
Test for Ammonia (NH₃)
Hold damp red litmus paper near gas
Positive result: Litmus paper turns blue
Test for Chlorine (Cl₂)
Hold damp blue litmus paper near gas
Positive result: Litmus paper turns red then white (bleached)
