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A student investigated the volume of sulfuric acid that reacted with 25 cm3 sodium hydroxide. Describe a titration method the student could use in this investigation. {6 marks}


My answer:

  1. Use the pipette and pipette filler to safely add 25 cm3 of $\ce{NaOH}$ to a clean conical flask.

  2. Add a few drops of indicator and put the conical flask on a white tile (so you can see the colour of the indicator more easily).

  3. Fill the burette with $\ce{H2SO4}$ and note the starting volume (record from bottom of the meniscus at eye level).

  4. Slowly add the acid from the burette to the alkali in the conical flask dropwise, swirling to mix.

  5. Stop adding the acid when the end-point is reached (the appropriate colour change in the indicator happens). Note the final volume reading of $\ce{H2SO4}$ (record from the bottom of the meniscus at eye-level).

  6. Repeat steps 1 to 5 until you get consistent readings


Have I missed anything that will prevent me from getting 6 marks?

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    $\begingroup$ I guess you haven't missed anything ..yet i would have mentioned an appropriate indicator for the reaction and mention the colour change ex:using phenolphthalein indicator until the colour changes from pink to colourless stable for 30 sec $\endgroup$ – Salma May 14 '17 at 20:28
  • $\begingroup$ Do not delete/repost questions $\endgroup$ – Mithoron May 15 '17 at 21:37
  • $\begingroup$ Usually the measurements also need to be stated to the specified precision of the instrument. For example, for my school's pipette, we typically give the measured quantity to 1 d.p. (i.e. 25.0 cm3) $\endgroup$ – Tan Yong Boon Nov 29 '18 at 23:40
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As titration is based on the relationship of molar quantity ($n$), volume ($V$) and concentration ($c$) of the reagents

$$ c = \frac{n}{V}$$

and as your titration is to determine the concentration of NaOH in a known volume of solution of analyte, you would need to know both the volume as well as the concentration of the $\ce{H2SO4}$ solution deployed by addition via the burette. The later is missing in your list.

Knowing the stoichiometry of the neutralisation is equally of importance, since each equivalent of $\ce{H2SO4}$ reacts with two equivalents of $\ce{NaOH}$. (This differs from a determination of, say, of / with $\ce{HCl}$, or $\ce{H3PO4}$.) Your current list neither accounts for a chemical equation, nor this stoichimetric factor.

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