Titration technique Knowledge-Based Download PDF

Questions

1. 1.

   Why must a funnel used to fill a buret be removed from the top of the buret before recording the initial volume and performing a titration?

   • A) Liquid remaining on the funnel can drip down into the buret during the titration, causing an error in the recorded volume of titrant dispensed.
   • B) An inserted funnel prevents atmospheric pressure from acting on the liquid surface, impeding the steady flow of titrant through the stopcock.
   • C) Leaving the funnel in place increases evaporation of the solvent from the buret, which alters the concentration of the titrant.
   • D) Contact between the glass funnel and the buret walls creates static electrical charges that disrupt the indicator endpoint transition.
2. 2.

   Why is a white tile or sheet of white paper placed beneath the Erlenmeyer flask during an indicator-based titration?

   • A) To insulate the reaction flask against heat transfer between the solution and the bench surface.
   • B) To provide a clear, neutral background that facilitates the detection of the faint initial color change at the endpoint.
   • C) To absorb chemical spills and prevent corrosive droplets from reacting with the laboratory benchtop.
   • D) To minimize parallax error when reading the liquid meniscus level inside the Erlenmeyer flask.
3. 3.

   During a titration, why can deionized water be used to rinse splashed analyte droplets from the inner walls of the receiving flask into the reaction mixture without altering the experimental result?

   • A) It adjusts the ionic strength of the mixture to keep the indicator transition range narrow.
   • B) It neutralizes residual acidic gases absorbed from the laboratory atmosphere during swirling.
   • C) It shifts the neutralization equilibrium forward, ensuring complete reaction of the titrant.
   • D) It changes the total volume of the solution without changing the amount of substance of the analyte.
4. 4.

   Why must any air bubble trapped in the buret tip below the stopcock be expelled before recording the initial volume and beginning a titration?

   • A) To prevent premature neutralization of the titrant solution before it contacts the analyte
   • B) To prevent an overestimation of the delivered titrant volume if the bubble escapes during titration
   • C) To ensure that the titrant stream maintains a constant volumetric flow rate throughout the analysis
   • D) To eliminate dissolved atmospheric gases that could alter the pH of the receiving analyte flask
5. 5.

   During the preparation of a buret for an acid-base titration, why is it essential to rinse the buret with small portions of the titrant solution after washing it with deionized water?

   • A) To dissolve and dislodge any persistent air bubbles trapped in the buret stopcock tip.
   • B) To neutralize any acidic or basic chemical residues remaining on the inner glass surfaces.
   • C) To prevent dilution of the standard titrant by residual droplets of deionized water.
   • D) To wet the internal glass walls so that the liquid meniscus aligns precisely with the graduation marks.