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Standardization of solutions used as acid-base titrants

Acid-base titration

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Acid-base titration » Standardization

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0.2M sodium hydroxide standardization against HCl

Sodium hydroxide solution can be standardized against hydrochloric acid solution of known concentration. This procedure is an easy and convenient one, especially taking into account fact, that hydrochloric acid solutions are very stable.

NaOH + HCl → NaCl + H2O

NaOH solution should be titrated against methyl orange or phenolphthalein. Indicator selection depends on the presence of carbonates in the sodium hydroxide solution. If the solution is carbonates free, end point volume will be identical in both cases. In the presence of carbonates, titration against phenolphtalein will end faster.

Standardization procedure to follow:

To make end point detection easier it is worth to prepare a comparison solution, identical to the titrated one; this way first color change is easier to spot.

To calculate sodium hydroxide solution concentration use EBAS - stoichiometry calculator. Download sodium hydroxide standardization against hydrochloric acid solution reaction file, open it with the free trial version of the stoichiometry calculator.

Click n=CV button in the upper (input) frame above HCl, enter volume and concentration of titrant, click Use. Click n=CV button below NaOH in the output frame, enter volume of the aliquot used, read solution concentration.

0.2M sodium hydroxide standardization against KHP

Sodium hydroxide solution can be standardized against potassium hydrogen phthalate (KHP). Reaction taking place during neutralization is

NaOH + KHC8O4H4 → KNaC8O4H4 + H2O

Standardization procedure to follow:

To calculate sodium hydroxide solution concentration use EBAS - stoichiometry calculator. Download sodium hydroxide standardization against solid KHP reaction file, open it with the free trial version of the stoichiometry calculator.

Enter KHP mass in the upper (input) frame in the appropriate mass edit field. Click n=CV button below NaOH in the output frame, enter volume of the solution used, read solution concentration.

0.2M hydrochloric acid standardization against sodium carbonate

Sodium carbonate is a salt of a weak acid. When titrated with hydrochloric acid carbonate decomposes, yielding carbon dioxide and water:

Na2CO3 + 2HCl → 2NaCl + CO2 + H2O

Evolving carbon dioxide acidifies the solution, and the end point in its presence is detected too early. To avoid titration errors we boil titrated solution to remove carbon dioxide.

Procedure to follow:

To make end point detection easier it is worth to prepare a comparison solution, identical to the titrated one; this way first color change is easier to spot.

To calculate hydrochloric acid solution concentration use EBAS - stoichiometry calculator. Download hydrochloric acid standardization against sodium carbonate reaction file, open it with the free trial version of the stoichiometry calculator.

Enter Na2CO3 mass in the upper (input) frame in the mass edit field above sodium carbonate formula. Click n=CV button below HCl in the output frame, enter volume of the solution used, read solution concentration.

0.2M hydrochloric acid standardization against borax

Borax has relatively high equivalent mass, which means potential errors in the standardization are smaller than in the case of other substances.

Reaction taking place during neutralization is

Na2B4O7 + 2HCl + 5H2O → 4H3BO3 + 2NaCl

Boric acid is so weak, that its presence doesn't interfere with end point detection (compare with standardization against sodium carbonate).

Procedure to follow:

To make end point detection easier it is worth to prepare a comparison solution, identical to the titrated one; this way first color change is easier to spot.

To calculate hydrochloric acid solution concentration use EBAS - stoichiometry calculator. Download hydrochloric acid standardization against borax reaction file, open it with the free trial version of the stoichiometry calculator.

Note, that to be consistent with the use of decahydrate molar mass and to be able to balance water, reaction equation is not the one shown above, but

Na2B4O7⋅10H2O + 2HCl → 4H3BO3 + 2NaCl + 5H2O

These are perfecly equivalent. Enter Na2B4O7·10H2O mass in the upper (input) frame in the mass edit field above borax formula. Click n=CV button below HCl in the output frame, enter volume of the solution used, read solution concentration.


Page was last modified on September 06 2009, 00:13:45.

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