You are told to dissolve citric acid in 75mL of distilled water. If you add 78 m

Question

You are told to dissolve citric acid in 75mL of distilled water. If you add 78 mL instead, what is the best course of action?

a. throw out the citric acid solution and make a new citric acid solution

b. evaporate some of the water until the volume of the citric acid solution is 75mL

c. Instead of dividing the moles of citric acid by .075L to get the molarity of the citric acid solution, divide by 0.078 L to get the molarity of the citric acid solution and proceed

d. increase the volume of sodium hydroxide solution by adding 3mL if water to compensate for the additional volume of the citric acid solution

e. increase the volume of the sodium hydroxide solution by adding 3 mL of 0.1 M NaOH solution to compensate for the additional volume of the citric acid solution.

Explanation / Answer

Water serves as solvent and it has no influence on the quantity of the acid or the titrating agent.
Also, the concentration of the titrating agent e.g.sodium hydroxide in this case must be known exactly(78mL), the amount of solvent is less important.

If you put 15 mL of sample in a 250 mL beaker and added 50 mL of water and titrated it, would you not have titrated all 15 mL? If you added 75 mL of water instead, but still only had 15 mL sample, would you still not have all of the sample titrated? The answer is, YES, you titrated all 15 mL of sample regardless of how much water you put in the beaker.

Dilution has nothing to do with the final titration of the sample. Dilution has everything to do with PREPARING the sample.

So , it is important to add 3mL of water to compensate the NaOH solution.

Well, in a titration it doesn't matter because in titration you are neutralizing the acid. In the neutralization the only thing that is important is the moles of acid in the solution as water is merely a neutral substance.

Therefore, no matter how much water you put in, it won't change how many moles of acid you need to neutralize by titration.

So the correct answer is d.

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