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Understanding acid-base titrations and calculations

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I am confused on how to calculate the concentratin of the HCl solution -
below are the answers so far that I have to get the final answer -please help. I am stumped on question 2 The concentration of the NaOH is known to be 0.1M

1. For your most exact titration, record the following:

(a) Volume of NaOH solution in the burette at the start (mL): 50ml

(b) Volume of NaOH solution in the burette at the end (mL): 32 ml

(c) Volume of NaOH solution delivered to the flask (mL): 18 ml

(d) Volume of HCl solution in the flask (mL): 20 ml

2. Calculate the molarity of the HCl concentration from the equation:

C(acid) = C(base) * V(base) / V(acid)

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Solution Preview

The "easy" answer to your question is to simply plug the numbers from question 1 into the equation shown in question 2. Doing so will definitely give you the "right" answer for the concentration of acid in this problem. Unfortunately, just plugging those numbers in to the equation makes it a little tricky to understand the concepts. So, here are two answers to your question. The first is "plug and play"; the second is an explanation of how the equation works.

"Plug and play" answer, using the provided equation:
C(acid) = C(base) * V(base) / V(acid)
Insert the concentration from the question & the volumes from your answers in part 1 of the question.
C(acid) = (0.1M)*(0.032L)/(0.020L)
Perform the calculation
C(acid) = ...

Solution Summary

The full solution is provided in two parts; first, a quick "plug and play" answer which demonstrates how to obtain the numerical answers; next, a full, step-by-step explanation of the principles involved, so that the student will gain a solid understanding of how and why the equation(s) work, when to apply them, and how to double check that the answer that is calculated is reasonable (very handy for exam situations). Exam hints / tips also included.

See Also This Related BrainMass Solution

Plotting a titration curve for Ala and His

Here is the problem:

1. Assume you have a solution containing 0.1 mol of Ala adjusted to pH = 0.5 with HCl. You begin adding 1.0 M NaOH. Plot (do not sketch) the resulting titration curve (pH vs. moles NaOH added) showing all inflection points. Show your calculations and be sure to state your assumptions.

2. Plot a similar titration curve for a solution containing 0.1 mol of His at pH = 0.5. (pKa values: Ala: alpha-COOH = 2.3, alpha-NH2 = 9.7; His: alpha-COOH = 1.8, alpha-NH2 = 9.2, Imidazole = 6.0).

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