Neutralisation

• What is the aim of the investigation described in the study material?

  To find the concentration of a dilute sulfuric acid solution using a sodium hydroxide solution of known concentration.
• What is the balanced chemical equation for the reaction between sulfuric acid and sodium hydroxide?

  H$_2$SO$_4$ + 2NaOH ----> Na$_2$SO$_4$ + 2H$_2$O
• What equipment is needed for the titration experiment?


  • 25 cm³ volumetric pipette
  • Pipette filler
  • 50 cm³ burette
  • 250 cm³ conical flask
  • Small funnel
  • Clamp stand and clamp
  • White tile
  • 0.1 M sodium hydroxide solution
  • Sulfuric acid
  • Phenolphthalein indicator
• How should you measure 25 cm³ of sodium hydroxide for the titration?


  Use the pipette to measure 25 cm³ of sodium hydroxide into the conical flask.
• Why is the conical flask placed on a white tile during the titration?


  To better observe the color change of the solution.
• What should be done after filling the burette with sulfuric acid?


  Record the initial reading of acid in the burette.
• How should the readings from the burette be taken?


  Always take readings from the bottom of the meniscus.
• How many drops of phenolphthalein indicator should be added to the conical flask?


  Add 5 drops of phenolphthalein indicator.
• What should be done while adding sulfuric acid from the burette?


  Slowly open the burette tap while swirling the conical flask.
• What indicates that you are near the endpoint of the titration?


  The color of the solution will start to change slightly.
• What color change occurs in phenolphthalein at the endpoint?

  The solution turns from pink to colorless.
• What should you do after observing a color change in the solution?

  Close the burette when a color change occurs in phenolphthalein.
• What is the next step after recording the final reading of acid in the burette?

  Calculate the titre, which is the volume of acid used to neutralize the alkali.
• What are concordant results in a titration?


  Results that are within 0.1 cm³ of each other.
• How should the results of the titration be presented?

  Present results in a table and calculate the mean titre, discarding any anomalies.
• How do you calculate the number of moles of sodium hydroxide used in the titration?


  By using the volume and concentration of sodium hydroxide.
• What is the ratio of sodium hydroxide to sulfuric acid in the balanced equation?


  The ratio is 2:1.
• How do you find the moles of sulfuric acid from the moles of sodium hydroxide?

  Divide the moles of sodium hydroxide by 2.
• What formula is used to calculate the concentration of sulfuric acid?

  Concentration = moles / volume (mean titre volume).
• What safety precautions should be taken when working with acids?

  • Wear safety goggles.
  • Tie hair back.
  • Report any broken glassware immediately.