CHAPTER 14: ANALYSIS FOR ACID + BASES

Question 1

volumetric analysis

Answer 1

• Technique used to accurately determine the unknown concentrations of acids and bases by reacting the solution with a solution of known concentration
• Unknown concentration determined based on the molar ratio in which chemicals react

Question 2

standard solution

Answer 2

• A standard solution is a solution of accurately known concentration.
• Prepared by dissolving primary standards in water
• are prepared in volumetric flasks

Question 3

primary standard

Answer 3

• be readily obtainable in a pure form
• have a known chemical formula
• be easy to store without deteriorating or reacting with the atmosphere
• have a high molar mass to minimise the effect of errors in weighing
• be inexpensive.

Acids: hydrated oxalic acid (H2C2O4.2H2O) and potassium hydrogen phthalate (KH(C8H4O4 ))

Bases: Sodium borate (Na2B4O6.10H2O) and anhydrous sodium carbonate (Na2CO3)

anhydrous: no water present

Question 4

preparing a standard solution errors

Answer 4

• parallax erors caused by shift in apparent position of an object due to viewing angle

Question 5

titrations

Answer 5

• used in acid-base chemistry
• given one KNOWN concentration
• uses molar ratio to work out unknwon concentration

Question 6

aliquots

Answer 6

unknown solution

Question 7

burette

Answer 7

• has the standard (known concentration) solution

Question 8

equivalence point

Answer 8

• the point at which the number of moles of both reactants are in exact proportions for a complete reaction.
• At the equivalence point only salt and water are present, making the solution neutral.

Question 9

end point

Answer 9

• point when a noticeable, permanent colour change is apparent
• An indicator that shows a colour change
  near the equivalence point should be selected
• A pH meter can be used instead of an
  indicator (more accurate)

Question 10

types of errors in titration

Answer 10

mistakes:
* misreading the numbers on a scale
* using a pipette of incorrect volume
* using a pipette of incorrect volume
* spilling a portion of a sample
* incorrect rinsing of glassware

Question 11

technique to maximise precision + accuracy

Answer 11

• burette + pipette: final rinse w/ acid or base they are to be filled with
• volumetric flask + conical flask: should only be RINSED with deionised water

Question 12

concordant titres

Answer 12

Three values within 0.10 mL of each other are averaged.