In which laboratory process could a student use 0.10 M NaOH(aq) to determine the concentration of an aqueous solution of HBr?
(1) chromatography
(2) decomposition of the solute
(3) evaporation of the solvent
(4) titration

2 Answer

  • (4) titration, the process of using an aqueous solution of known concentration to determine the concentration of another solution of unknown concentration, is your answer.
  • Answer:

    4) titration


    Titration is a standard process used in a laboratory to determine the concentration of an unknown analyte. A titrant of known concentration is gradually added to a known volume of the analyte in the presence of a suitable indicator. The end of the titration is marked by a color change of the analyte.

    The given example is that of an acid(HBr) - base(NaOH) titration which can be represented by the following equation:

    NaOH + HBr → NaBr + H2O

    Thus  1 mole of acid gets neutralized by 1 mole of the base to form 1 mole of the salt (NaBr)

    Let M1 and V1 are the molarity and volume of the base (NaOH). Here, the molarity of NaOH is known = M1 =  0.10 M and the volume, V1 corresponds to the end point in the titration.

    M2 and V2 are the molarity and volume of HBr. Here, V2 is  known whereas M2 needs to be determined.

    Based on the reaction stoichiometry:

    moles of NaOH = moles of HBr

    [tex]M1*V1=M2*V2\\\\Therefore,\\\\M2 = \frac{M1*V1}{V2}[/tex]