Practicals

• What is an independent variable in an experiment?

  The variable that is changed
• What is a dependent variable in an experiment?

  The variable that changes as a result
• Why do we control variables in experiments?

  To ensure accurate results
• What should you always state when measuring?

  The equipment used for each measurement
• Why is it important to mention safety precautions in experiments?

  To ensure safety while working with chemicals
• What should you do to reduce parallax error when measuring?

  Align your eye with the measurement
• Why is it beneficial to take multiple measurements?

  To calculate a mean and reduce errors
• How should answers be formatted in practical reports?

  In bullet point format for clarity
• How should you phrase instructions in a practical report?

  Use proper English and clear instructions
• What is the process for making salt crystals?

  1. Heat concentrated sulfuric acid in a beaker.
  2. Add excess copper oxide until unreacted powder remains.
  3. Filter out unreacted copper oxide.
  4. Gently heat the copper sulfate solution in an evaporating basin.
  5. Collect solid crystals of copper sulfate.
• What is electrolysis?

  A chemical reaction caused by electricity
• What type of electrodes are used in electrolysis?

  Inert carbon electrodes
• What happens at the cathode during electrolysis?

  A positive ion is reduced
• What happens at the anode during electrolysis?

  A negative ion is oxidized
• What occurs if the cation is more reactive than hydrogen?

  Hydrogen is reduced to form H2 gas
• What gas is produced at the anode when chloride ions are present?

  Chlorine gas (Cl2)
• What happens when sodium sulfate is electrolyzed?

  Oxygen gas is produced at the anode
• How do temperature changes affect reactions?

  1. Conduct reaction in a polystyrene cup.
  2. Use a thermometer to measure maximum temperature.
  3. Vary the volume of the alkali as the independent variable.
  4. Record temperature changes to find neutralization point.
• What are the methods to observe rates of reaction?

  1. Measure gas volume produced over time.
  2. Observe cloudiness in a reaction mixture.
  3. Change conditions like temperature or concentration.
• What is the process of chromatography?

  1. Place a spot of mixture on chromatography paper.
  2. Draw a pencil line as a reference.
  3. Hang paper in distilled water to allow diffusion.
  4. Calculate RF values to identify substances.
• What is desalination?

  The removal of salt from water
• What is the purpose of distilling water?

  To obtain pure, potable water
• What is the process of titration?

  1. Measure a specific volume of alkali in a flask.
  2. Add an indicator to the alkali.
  3. Fill the burette with acid and add dropwise.
  4. Swirl until the solution remains pink.
  5. Calculate concentration using moles and volume.
• What indicates the presence of carbonate ions?

  Bubbles when hydrochloric acid is added
• How can metal and non-metal ions be identified?

  1. Use flame tests for metals.
  2. Test for carbonate ions with hydrochloric acid.
  3. Use silver nitrate for halide ions.
  4. Test for sulfate ions with barium chloride.
• What forms when chloride ions are tested with silver nitrate?

  A white precipitate
• What forms when bromide ions are tested with silver nitrate?

  A cream precipitate
• What forms when iodide ions are tested with silver nitrate?

  A yellow precipitate
• What indicates the presence of sulfate ions?

  A white precipitate with barium chloride
• What should be avoided in purified water tests?

  Positive tests for sodium or chloride ions
• Why is it important to use proper English in practical reports?

  To ensure clarity and professionalism
• Why should safety precautions be stated clearly?

  To prevent accidents during experiments
• What is the significance of parallax error in measurements?

  It can lead to inaccurate readings
• Why is repeating measurements important for reliability?

  It helps to identify consistent results
• How do you calculate RF values in chromatography?

  Distance solute moves / distance solvent moves
• What is the procedure for conducting a titration accurately?

  Measure alkali, add acid dropwise, swirl
• What is the role of indicators in titrations?

  To show when neutralization occurs
• What is the method for preparing copper sulfate crystals?

  Neutralize acid with excess base, filter
• What is the significance of water distillation?

  To obtain pure, drinkable water
• What does cloudiness in reaction mixtures indicate?

  Increase in product formation