Experiment 8: pH TITRATION OF WEAK The previous experiment demonstrated the appl

Question

Experiment 8: pH TITRATION OF WEAK The previous experiment demonstrated the application of standard titration quantitatively determining the contents of mixtures. An indicator was used e hniques for titrations to reveal, by means of a color change, when the squivalence point (neutralization point) was reached, that is, when sufticient titrant had been added with all of the analyte. You will explore in this experiment an alternative appr titration, one in which a pli probe and data acquisition system are employed to monto r was used in thes for to react the progress of the reaction. Consider the titration of 25 mL of 0.10 MHC,H,O (a weak acid) with 0.10 M strong base): NaOH (a + NaOH NaC,H,O;+HO Because the concentrations of the analyte (the acetic acid) and titrant (the base) are equal, and because the stoichiometry of the analyte and titrant is 1:1, we know that 25 mL of the NaOH solution will be required to reach the equivalence point. Now suppose that we follow the pH of the acid solution as the NaOH is slowly added to it. The result would be the titration curve shown in Figure 1. The acid solution has a low initial pH (2.87). As 14 T 12 10 10 20 mL NaOH 30 40 Figure 1. pH titration curve for titrating 25 mL 0.10 MHC,H,0, with 0.10 M NaOH.

Explanation / Answer

Number of moles of NaOH = Volume in L * molarity

= 16.09 /1000 * 0.09699

= 0.00156 mole NaOH

The reaction of KHP and NaOH as follows:

KHP + NAOH = H2O + NAKP

Now calculate the moles of KHP;

0.001561 mole NaOH * 1 mole KHP/1 Mole NaOH

= 0.001561 mole KHP

We know that, number of moles = amount in g/ molar mass

Molar mass = amount in g/ number of moles

= 0.300 g/ 0.00156 moles

= 192.31 g/ mole

This is experimental value

The molar mass of KHP is 204.22 g/mol

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