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Suppose you perform a titration of an unknown weak acid solution. You start with 4.00 mL of the weak acid and find that it takes 14.2 mL of 0.0500 M NaOH to reach the equivalence point. What is the concentration of the unknown weak acid solution

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Answer:

0.1775 M

Explanation:

The reaction that takes place is:

  • HA + NaOH → NaA + H₂O

Where HA is the unknown weak acid.

At the equivalence point all HA moles are converted by NaOH. First we calculate how many NaOH moles reacted, using the given concentration and volume:

  • 0.0500 M NaOH * 14.2 mL = 0.71 mmol NaOH

That means that in 4.00 mL of the weak acid solution, there were 0.71 weak acid mmoles. With that in mind we can now calculate the concentration:

  • 0.71 mmol HA / 4.00 mL = 0.1775 M

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