An unknown weak acid (weak Acid Mij is titrated with standardized NaoH (0.4477 M

Question

An unknown weak acid (weak Acid Mij is titrated with standardized NaoH (0.4477 M NaoH) and gives the following weak acid titration (pH vs vuon and First Derivative' (ApH/AvNoe vs. v No) curv Titration of Weak Acid #1: pH vs, Volume of NaOH Titrant 13.0 12.00 11.00 10.0 9.0 7.0 6,0 5.0 4.0 3.0 2.0 0.00 1.00 2.000 3,000 4.00 5.000 6,000 7.000 9.00 10.00 volume of NaoH (mL) Titration of Weak Acid A1 First Derivative' vs. Volume of NaOH Titrant 350 250 150 0.00 1.000 2.00 3000 4.00 5.000 6.00 7.000 8.00 9.00 10.00 Volume of NaoH (mL) Question 1 (1 p From the curves, what is the VNoor volume of titrant base at the equivalence point for weakAcid it1?

Explanation / Answer

According to the graph, volume of NaOH required to reach equivalence point = 4.4 mL

volume of NaOH to reach the equivalence point = 2.2 mL

pH at half equivalenc point = 5. So, pKa = 5

moles of NaOH added to equivalence point = moles of weak acid present

moles of NaOH = 0.4477 M * 0.0044 L = 1.97 *10^-3 moles

moles of acid used in the titration = 1.97 *10^-3 moles

molar mass of the acid = mass of acid /1.97 *10^-3 moles = 0.117g/1.97 *10^-3 moles = 59.4 g/mol

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