Chemistry: Chemical tests

    Cards (37)

    • What are anions?
      Negatively charged ions
    • What happens when a carbonate reacts with an acid?
      It forms a salt, carbon dioxide gas, and water
    • How can you test for the presence of carbonates in a solution?
      Add dilute hydrochloric acid and bubble the gas produced through lime water
    • What indicates a positive test result for carbonates when using lime water?
      If the lime water turns cloudy
    • What is the test for sulfates based on?
      The reaction of barium ions with sulfate ions to form barium sulfate
    • What is the appearance of barium sulfate when formed?
      It is a white precipitate
    • What must be done before adding barium ions to test for sulfates?
      Add dilute hydrochloric acid to remove carbonate or sulfite ions
    • Why is it important to remove carbonate or sulfite ions before testing for sulfates?
      To avoid confusion from unwanted white precipitates
    • What is the first step in the test for halide ions?
      Add dilute nitric acid to remove carbonate and sulfite impurities
    • What is added in the second step of the halide test?
      Add silver nitrate
    • How does the color of the precipitate help identify halide ions?
      The color indicates which halide ion is present
    • What color precipitate forms with chloride ions?
      White precipitate (silver chloride)
    • What color precipitate forms with bromide ions?
      Cream precipitate (silver bromide)
    • What color precipitate forms with iodide ions?
      Yellow precipitate (silver iodide)
    • What is the process for testing for halide ions?
      1. Add dilute nitric acid to remove impurities.
      2. Add silver nitrate to the sample.
      3. Observe the color of the precipitate:
      • White for chloride
      • Cream for bromide
      • Yellow for iodide
    • What does the term 'cation' refer to?

      A positively charged ion
    • Which of the following ions is an example of a cation?
      Mg2+^{2+}
    • Why are nearly all cations metal ions?
      Because metals form positive ions
    • What is the only common exception to the rule that cations are metal ions?

      The ammonium ion, NH4+_{4}^{+}
    • What are the two groups of tests for cations?
      • Flame tests
      • Metal hydroxide tests
    • What are the steps to perform a flame test?
      1. Clean a platinum (or nichrome) wire loop with dilute hydrochloric acid and rinse with distilled water.
      2. Heat the wire loop over a Bunsen burner flame.
      3. Dip the wire loop into the compound to be tested.
      4. Hold the wire loop in the clear blue part of the Bunsen burner flame.
      5. Observe the color of the flame.
    • What color flame do lithium ions (Li+^{+}) produce?

      A crimson flame
    • What color flame do sodium ions (Na+^{+}) produce?

      A yellow flame
    • What color flame do potassium ions (K+^{+}) produce?

      A lilac flame
    • What color flame do calcium ions (Ca2+^{2+}) produce?

      An orange-red flame
    • What color flame do copper ions (Cu2+^{2+}) produce?

      A green flame
    • What is a limitation of the flame test?
      Colors of flames may mix if there are multiple metals in the sample
    • How does the metal hydroxide test work for identifying metal ions?
      • React metal ions with sodium hydroxide (NaOH)
      • Observe the color of the solution or precipitate formed
      • Some metal ions form colored precipitates with hydroxide ions
    • What color precipitate does copper(II) form when reacted with hydroxide ions?
      A blue precipitate
    • What color precipitate does calcium form when reacted with hydroxide ions?
      A white precipitate
    • What color precipitate does iron(II) form when reacted with hydroxide ions?
      A green precipitate
    • What color precipitate does iron(III) form when reacted with hydroxide ions?
      A brown precipitate
    • What color precipitate does magnesium form when reacted with hydroxide ions?
      A white precipitate
    • What color precipitate does aluminium form when reacted with hydroxide ions?
      A white precipitate that redissolves to form a colorless solution with excess NaOH
    • Sulphuric acid test - white fumes (SO2)
    • Iodine solution test - brown/black precipitate
    • Bromine water test - purple colour
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