Chemical Analysis

• What is a pure substance?

  A single element or compound not mixed
• What are formulations?

  Mixtures designed as useful products
• What effects do impurities have on boiling and melting points?

  • Increase boiling point
  • Decrease melting point
  • Increase melting range
• What is an active ingredient in a formulation?

  The main ingredient producing the desired outcome
• Why might tablets contain inactive ingredients?

  To allow better absorption of the medicine
• Why do tins of the same color paint need consistent ingredients?

  To ensure the color remains the same
• How does the heating curve differ for pure and impure substances?

  Pure substances have a set melting/boiling point
• What is a formulation?

  A mixture designed as a useful product
• Describe the steps of chromatography.

  1. Hang chromatography paper in a beaker
  2. Draw a pencil line on the paper
  3. Add ink spots on the pencil line
  4. Label each spot
  5. Pour water into the beaker
  6. Lower the paper into the water
  7. Wait until water reaches the top
  8. Mark the solvent front before drying
• What is chromatography used for?

  To separate colored compounds in a mixture
• What is the mobile phase in chromatography?

  The solvent that moves through the stationary phase
• What happens if a substance travels far in chromatography?

  The attraction to the mobile phase is stronger
• What indicates the presence of hydrogen gas?

  A lighted splint makes a popping sound
• How do you test for oxygen gas?

  A glowing splint relights in oxygen
• How do you test for carbon dioxide gas?

  Bubble gas through limewater to check for cloudiness
• What happens to limewater when carbon dioxide is present?

  Limewater turns cloudy
• How do you test for chlorine gas?

  Damp litmus paper turns white when exposed
• What are the steps to test for chlorine gas?

  1. Add damp litmus paper to the gas
  2. Observe if it turns white
  3. If it turns white, chlorine is present
• What are the phases in chromatography?

  • Mobile phase: solvent moving
  • Stationary phase: chromatography paper
• What indicates strong attraction between a substance and the mobile phase in chromatography?

  The substance travels far up the paper
• What is the purpose of a flame test?

  To identify positive ions in a compound
• What are the steps for testing positive ions using a flame test?

  1. Light a Bunsen burner
  2. Dip a wire loop in the sample
  3. Hold it in the flame
  4. Observe and record the flame color
• What color flame indicates sodium ions?

  Yellow
• What color flame indicates potassium ions?

  Lilac
• What color flame indicates lithium ions?

  Crimson
• What color flame indicates calcium ions?

  Orange-red
• What is the procedure for testing for negative ions?

  1. Add dilute nitric acid to the sample
  2. Follow with silver nitrate solution
  3. Observe the color of any precipitate formed
• What color precipitate indicates chloride ions?

  White
• What color precipitate indicates bromide ions?

  Cream
• What color precipitate indicates iodide ions?

  Yellow
• What is the test for sulfate ions?

  1. Add dilute hydrochloric acid
  2. Follow with barium chloride solution
  3. Observe for white precipitate
• What are the advantages and disadvantages of instrumental methods?

  Advantages:

  • Highly accurate and sensitive
  • Fast analysis
  • Small sample sizes

  
  

  Disadvantages:

  • Expensive
  • Requires special training
  • Results need comparison with known samples
• What is flame emission spectroscopy used for?

  To analyze wavelengths of light produced
• Why are instrumental methods useful in environmental testing?

  They identify pollutants in small amounts
• What is the formula for testing carbonate ions?

  CO3²⁻ + 2H⁺ → CO2 + H2O
• What happens when you add acid to carbonate ions?

  Effervescence occurs, producing carbon dioxide
• How do you test for halide ions?

  Add dilute nitric acid followed by silver nitrate
• What color precipitate indicates the presence of sulfate ions?

  White precipitate with barium chloride
• What is the purpose of using limewater in gas tests?

  To check for carbon dioxide presence
• What is the result of bubbling gas through limewater?

  Limewater turns cloudy if CO2 is present