Abstract This paper is a technical report on a laboratory experiment on surface tension measurements using the capillary rise method. Samples are deionized water and varying concentrations of NaCl and of HOAc. Calculations are included in the appendix.
From the Paper "Increasing concentrations of HOAc solutions tend to lower surface tension of water, while NaCl solutions increase surface tension of water. The former results to a condition called positive surface concentration, where the solute tend to concentrate slightly in the neighborhood of the surface; the latter is due to negative surface concentration, where the solute molecules become less concentrated in the neighborhood of the surface."
Abstract The paper relates the method, procedure and observations of an experiment that uses the titration method to obtain accurate measurements of reactants in a chemical reaction. The paper provides the calculations of the concentration of sodium hydroxide and notes the sources of error that could have been prevented.
Outline:
Introduction
Materials
Procedure
Observations
Calculations
Sources of Error
From the Paper "A titration is a method used by people all over the world to obtain accurate measurements of both reactants in a chemical reaction. Generally some sort of indicator or pH scale is used to determine when the exact moment is that the reaction is complete. In doing this, the measurement of the titrant becomes more precise, and later calculations can be made at a more exact value. Phenolphthalein is used as an acid and base indicator as it causes a solution to change colour, either pink or colourless, as a solution becomes a base or an acid, respectively. The alteration between the pink colour and colourless is at around a pH of 9. When the pH is above approximately 9 then the phenolphthalein will cause a solution to become pink and when the pH is below approximately 9 the phenolphthalein will cause the solution to become colourless. A titrant is a solution placed in the buret, which is attached to a retort stand with a clamp."
