2

• What apparatus is used to measure volumes in a titration?

  Burette
• What is the purpose of a pipette in a titration?

  To measure a specific volume of solution
• Describe the 'weighing-by-difference' method.

  Weigh substance, transfer, reweigh, calculate difference
• What is the first step in the 'weighing-by-difference' method?

  Add roughly the desired mass to a weighing bottle
• What should you do after transferring the substance in the 'weighing-by-difference' method?

  Reweigh the weighing bottle
• What is the final calculation in the 'weighing-by-difference' method?

  The difference between the masses is the mass of solid
• What are the steps to carry out an acid-base titration?

  1. Use a pipette to add 25 cm³ of acid to a conical flask and add indicator.
  2. Pour alkali into the burette and record the initial volume.
  3. Complete a trial titre, swirling the flask, and record the final volume.
  4. Repeat until two concordant results are obtained, adding alkali drop by drop near the end point.
• How can you ensure maximum transfer of a dissolved substance between beakers?

  Use distilled water to wash leftover solution
• How do you accurately fill a volumetric flask to the graduated mark?

  Fill until the bottom of the meniscus rests on the mark
• What is a standard solution?

  A solution of a known concentration
• Describe how to make a standard solution of NaHCO3.

  1. Weigh out a specified amount of NaHCO3.
  2. Add a small volume of distilled water to dissolve it.
  3. Use a funnel to add the solution to a 250 cm³ volumetric flask.
  4. Rinse the beaker with distilled water and add the washings to the flask.
  5. Make the flask up to the graduation mark with distilled water.
  6. Stopper and shake the flask.
• Name two indicators that could be used in an acid-base titration.

  Phenolphthalein and Methyl orange
• What is the color of phenolphthalein in acidic conditions?

  Colorless
• What is the color of phenolphthalein in basic conditions?

  Pink
• What is the color of methyl orange in acidic conditions?

  Red
• What is the color of methyl orange in basic conditions?

  Yellow
• What are concordant results in a titration?

  Titres within 0.1 cm³ of each other
• To what precision should burette readings be recorded?

  To the nearest 0.05 cm³
• Which results are used to calculate a mean titre?

  Two concordant results
• What apparatus helps observe color change during a titration?

  A white tile
• What are the three requirements for taking an accurate burette reading?

  1. Read from the bottom of the meniscus.
  2. Allow liquid on the walls to settle.
  3. Ensure there are no air bubbles.
• What is the end point of a titration?

  The first point where the indicator changes color permanently
• Why is the conical flask swirled during a titration?

  To ensure all reactants are combined
• Why is a titre volume of 25 cm³ better than 10 cm³?

  Smaller percentage error with larger volume
• What equation links number of moles and concentration?

  Number of moles = concentration x volume
• How do you calculate the concentration of acid from the volume of acid required to neutralize an alkali?

  1. Calculate moles of alkali (n = C x V).
  2. Use the chemical equation for the acid-alkali ratio.
  3. Divide moles of acid by the volume used in neutralization.