Exercise 13.23

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Amy Wu 1D
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Exercise 13.23

Postby Amy Wu 1D » Tue Aug 01, 2017 3:58 pm

"13.23 (a) Sketch the titration curve for the titration of 5.00 mL 0.010 m NaOH(aq) with 0.005 m HCl(aq), indicating the pH of the initial and final solutions and the pH at the stoichiometric point. What volume of HCl has been added at (b) the stoichiometric point; (c) the halfway point of the titration?"

Can someone explain to me how to go about this problem? I have a hard time conceptualizing the calculations, especially at the stoichiometric point, and Example 13.4 is not helping much.

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Re: Exercise 13.23

Postby Chem_Mod » Wed Aug 02, 2017 12:22 am

Anytime you have a titration problem, your first step needs to be: M(acid)V(acid) = M(base)V(base) to determine the volume of titrant added to reach the endpoint.

In this example: (.005M)(x) = (.010M)(5.00ml) so x = .100 ml at the endpoint. Therefore, the halfway point must be at 0.0500ml.

To solve for the initial pH, it is a normal equilibrium calculation. Set up the Ka or Kb and solve for the H+ or OH-, respectively. Then solve for pH.
To solve for the pH at the halfway point, use the formula pH = pKa.
To solve for pH at the endpoint, set up an ICE box and again solve for the H+ or OH- and use those values to then solve for pH.

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