Question 1: Define a titration and explain its purpose in quantitative chemistry.

Answer: A titration is a laboratory technique used to determine the concentration of an unknown solution by reacting it with a solution of known concentration, using a burette to add the known solution until the reaction is complete.

Question 1: What is the colour change observed in an acid-alkali titration using phenolphthalein as an indicator?

Answer: The solution changes from colourless to pink as the alkali is in excess.

Question 2: Describe the role of the burette in a titration.

Answer: The burette accurately measures and delivers the known volume of titrant (solution of known concentration) during the titration process.

Question 1: A 25.0 cm³ sample of hydrochloric acid (HCl) reacts with 30.0 cm³ of sodium hydroxide (NaOH) of concentration 0.100 mol/dm³. Calculate the concentration of the hydrochloric acid.

Answer: 0.120 mol/dm³

Question 2: During a titration, 20.0 cm³ of sulphuric acid (H₂SO₄) required 40.0 cm³ of 0.250 mol/dm³ sodium carbonate (Na₂CO₃) to neutralise. Calculate the concentration of the sulphuric acid.

Answer: 0.125 mol/dm³

Question 1: List three variables that can affect the accuracy of a titration and suggest a method to minimise each.

Answer: Variables include: (1) Misreading the burette - minimise by reading at eye level; (2) Incomplete mixing - ensure thorough swirling; (3) Using incorrect indicator - select the appropriate indicator for the reaction.

Question 2: Describe the safety precautions that should be observed during titration experiments.

Answer: Wear safety goggles to protect eyes, handle acids and alkalis with care to prevent spills and burns, and dispose of chemical waste according to safety guidelines.

Question 1: A titration experiment recorded a titre volume of 24.5 cm³. If the known concentration of the titrant is 0.050 mol/dm³, what is the amount of substance reacted? Show your working.

Answer: 6.13 × 10⁻⁴ mol

Question 2: A student consistently records titre volumes higher than the actual endpoint, leading to a systematic error. Explain how this affects the calculated concentration of the unknown solution and suggest a way to correct it.

Answer: This systematic error causes the calculated concentration to be higher than the true value because the student overestimates the volume needed. To correct it, the student should calibrate their equipment carefully and ensure accurate reading at eye level.

Question 1: Explain how titrations are used in the pharmaceutical industry to ensure the correct dosage of medicines.

Answer: Titrations are used to determine the concentration of active ingredients in medicines, ensuring each dose contains the correct amount for safety and efficacy.

Question 2: Describe a modern technological advancement that has improved the accuracy of titration measurements.

Answer: Automated titration systems with digital sensors and precise volume measurements have improved accuracy and reproducibility compared to manual titrations.