chem test y11

• How do ionic compounds conduct electricity when dissolved in water?

  Their ions are free to move and carry charge
• What are solutions of ionic compounds in water called?

  Electrolytes
• What is the process of electrolysis?

  Passing an electric current through an electrolyte
• What happens to ions during electrolysis?

  They move to electrodes and undergo reactions
• What occurs at the cathode during electrolysis of molten ionic compounds?

  Positive metal ions gain electrons
• What occurs at the anode during electrolysis of molten ionic compounds?

  Negative non-metal ions lose electrons
• What are the products of electrolysis of molten lead bromide?

  Lead at the cathode and bromine at the anode
• Why are some metals extracted using electrolysis instead of carbon?

  They are more reactive than carbon
• What is produced at the cathode in aqueous electrolysis if the metal is more reactive than hydrogen?

  Hydrogen gas
• What is produced at the anode in aqueous electrolysis if halide ions are present?

  The halogen is produced
• What is the procedure for investigating aqueous solutions using inert electrodes?

  • Set up inert electrodes in a beaker
  • Connect to a power supply
  • Observe and test gases/products formed
• What occurs at the anode during electrolysis?

  Oxidation occurs (loss of electrons)
• What occurs at the cathode during electrolysis?

  Reduction occurs (gain of electrons)
• Write the balanced half equation for the reduction of lead ions in molten lead bromide.

  Pb²⁺ + 2e⁻ → Pb
• Write the balanced half equation for the oxidation of bromide ions in molten lead bromide.

  2Br⁻ → Br₂ + 2e⁻
• What defines a pure substance?

  It has a fixed melting and boiling point
• How can mixtures be identified from melting and boiling points?

  They melt or boil over a range of temperatures
• What is chromatography used for?

  To separate mixtures into components
• What do dots on a chromatogram represent?

  Individual substances in a mixture
• How does paper chromatography separate substances?

  Based on solubility and interaction with solvent
• What does a pure substance produce in chromatography?

  One spot on the chromatogram
• What does the Rf value represent?

  Distance travelled by substance ÷ distance travelled by solvent
• How do Rf values differ in different solvents?

  They differ due to solubility
• What is the procedure for paper chromatography to separate substances?

  • Draw a baseline on paper
  • Place ink dots on the baseline
  • Dip the paper in solvent
  • Measure distances and calculate Rf values
• How do you test for hydrogen gas?

  Use a lit splint that pops
• How do you test for oxygen gas?

  Use a glowing splint that relights
• How do you test for carbon dioxide?

  It turns limewater cloudy
• How do you test for chlorine gas?

  It bleaches damp litmus paper white
• How can metal ions be identified using flame tests?

  By observing the color of the flame
• What color flame indicates lithium ions?

  Crimson
• What color flame indicates sodium ions?

  Yellow
• What color flame indicates potassium ions?

  Lilac
• What color flame indicates calcium ions?

  Orange-red
• What color flame indicates copper ions?

  Green
• How does sodium hydroxide identify metal ions?

  By forming colored precipitates
• What color precipitate does aluminium form with sodium hydroxide?

  White (dissolves in excess)
• What color precipitate does copper(II) form with sodium hydroxide?

  Blue
• What color precipitate does iron(II) form with sodium hydroxide?

  Green
• What color precipitate does iron(III) form with sodium hydroxide?

  Brown
• Write the balanced equation for the reaction of copper ions with hydroxide ions.

  Cu²⁺(aq) + 2OH⁻(aq) → Cu(OH)₂(s)