Introduction
Standardization is the process of testing a solution of unknown concentration with a solution of a known, precise concentration. The NaOH Standardization Calculator determines the normality of your sodium hydroxide (NaOH) solution from the titration of a potassium hydrogen phthalate (KHP) solution of known normality.
There are a number good reasons to test your solution of sodium hydroxide (NaOH) prior to titrating your wine. First, NaOH solutions lose strength over time due to exposure to CO2 in the air. Second, NaOH solutions are virtually impossible to prepare to a precise molar concentration because the substance is hygroscopic (in other words, it absorbs moisture from the air) so a measured sample of the compound is never 100% NaOH. On the other hand, the acid salt potassium hydrogen phthalate, KHC8H4O4 or KHP, is not hygroscopic, so it can be measured out in precise mass amounts.
Input Field Definitions
KHP Volume – The volume of KHP solution being titrated.
KHP Normality – The normality of the KHP solution being titrated.
Volume of NaOH Added – The volume of NaOH solution required to reach the titration endpoint.
Output Field Definitions
NaOH Normality – The calculated normality of the NaOH solution.
Calculation Details
The reaction equation for the standardization titration is.
KHC8H4O4 + NaOH —> KNaC8H4O4 + H2O |
(3-26) |
Since KHP reacts with NaOH in a simple 1:1 stoichiometric ratio, we can write the following molar balance:
vnNn = vkNk |
(3-27) |
where:
vn = volume of NaOH sample, liters
Nn = normality of NaOH sample, moles/liter
vk = volume of KHP sample, liters
Nk = normality of KHP sample, moles/liter
Rearranging equation (3-27) to solve for the NaOH normality gives:
Nn = vkNk/vn |
(3-28) |
To perform the standardization titration, measure a small volume (5-10 mL) of the KPH into a water glass or flask. Add about 5 drops of phenolphthalein indicator to the sample. Titrate with your NaOH until the end is reached, which is the first pink blush that persists for at least 20 seconds after mixing the sample. Make note of how much NaOH was used, and enter the values into FermCalc to determine the normality of your NaOH.