Accounting for DI Water during Titration

In summary: This is lab reality.In summary, the conversation discusses calculating the molarity of a sodium hydroxide solution based on titration results. The question of how to account for the DI water in the titration process is raised, with the naive approach being subtracting the NaOH required for the DI titration from the NaOH required for the KHP titration. However, it is noted that this may not be accurate in all cases and the best approach is to dissolve the KHP in the same volume of DI water as the sample. Overall, the question is poorly designed and there is no clear answer.
  • #1
giacomh
36
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So I've gotten close to the correct answer for this problem, but I think I'm accounting for the DI water incorrectly:

In titrating a blank, 0.11 mL of sodium hydroxide solution was required to titrate 50.00 mL of DI water. It required 17.56 mL of the same sodium hydroxide solution to titrate 0.7711 g of potassium hydrogen phtalate (KHC8H4O4) dissolved in 20.00 mL of D water. Calculate the molarity of the NaOH solution.

I accounted for the DI water by simply subtracting the NaOH required for the DI titration from the NaOH required for the KHP titration. I think I need to account for the change in volume? Not sure how to do that...

My attempt:

17.56mL - .11 mL = .1745 mL
.7711 g / 204.2234 g/mol = .003776 mol
.003776 mol/ .01745 L = .2164 M


Thanks!
 
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  • #2
Hard to say.

Naive approach would call for assuming if 50 mL required 0.11 mL for a blank, 20 mL will require 20/50*0.11 mL. But it doesn't have to be true, as blank can require a constant volume (for example used to change color of the indicator) and/or volume of titrant that depends on the volume of the sample. In lab reality you should dissolve KHP in 50 mL, then it would not matter what the blank is really needed for. (Actually in lab reality I would dissolve KHP separately to be able to repeat the titration, but that's another story).

As the question is poorly designed, there is no good answer here. What you did is what I would do, whether it is what the person asking the question had on mind I have no idea.
 

FAQ: Accounting for DI Water during Titration

1. What is the purpose of accounting for DI water during titration?

The purpose of accounting for DI water during titration is to ensure accurate and precise results. DI water, or deionized water, is free of any ions or impurities that could potentially affect the outcome of the titration. By accounting for the amount of DI water used, the concentration of the titrant can be accurately calculated.

2. How do you account for DI water during titration?

To account for DI water during titration, the volume of DI water added to the titration flask must be measured and recorded. This volume is then subtracted from the total volume of the titration solution to obtain the volume of titrant used. The concentration of the titrant can then be calculated using this adjusted volume.

3. What is the importance of using DI water in titration?

Using DI water in titration is important because it helps to eliminate any potential sources of error. DI water is free of ions and impurities, which can affect the reactivity and concentration of the titrant. By using DI water, the results of the titration will be more accurate and reliable.

4. Can other types of water be used in titration instead of DI water?

Other types of water, such as tap water or distilled water, can be used in titration. However, these types of water may contain ions or impurities that could affect the outcome of the titration. It is recommended to use DI water for the most accurate and reliable results.

5. Is it necessary to account for DI water in all types of titrations?

Yes, it is necessary to account for DI water in all types of titrations. DI water should be used as the solvent for the titration, and its volume must be taken into consideration to obtain accurate results. Whether it is an acid-base titration or a complexometric titration, accounting for DI water is essential for obtaining precise results.

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