QUESTION 1 Student X completed Experiment O (pH-Titration Curves) by following t

Question

QUESTION 1 Student X completed Experiment O (pH-Titration Curves) by following the procedure in the lab manual but her pH-titration curve revealed that she accidentally titrated unknown monoprotic weak acid (HA), instead of the HCl solution. As shown in Figure la, student X observed that straight lines drawn through the data points in regions before and after the equivalence point intersected the straight line drawn through the data points in the equivalence point region at (28.99 mL, 5.23) and (29.25 mL, 11.84). Student X also found that the initial point of the titration curve was at (0.00 mL, 2.21) and the initial acid was halfneutralized at (14.56 mL. 4.21). Figure 1a: Titration of 20.00 mL of Unkown Weak Acid Using 0.4217 mol/L NaOH(aq) 14.0 29.25,11.84 12.0 10.0 8.0 6.0 4.56,4.21 28.99,5.23 4.0

Explanation / Answer

The equivalence point is defined as the point where the moles of strong acid added = initial moles of base B in solution. Graphically, the equivalence point is where the curve is most vertical.

The pH starts off low and increases as you add more sodium hydroxide solution. the pH doesn't change very much until you get close to the equivalence point. Then it surges upwards very steeply.

At equivalence point PH of solution is 7

So, from the the volume of NaOH used is around 29.00 ml to 29.10 ml

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