# Do we need to standardize 10M of NaOH?

I made $10~\mathrm{M}$ of $\ce{NaOH}$ solution by diluting $40~\mathrm{g}$ of its pellets in distilled water. I'm not sure if it's really $10~\mathrm{M}$ or at least close enough, but I don't think standardize can be done in such concentration. I've been careful enough in making the solution such as measuring the mass in low humidity room and closing it with plastics/glass.

## 1 Answer

This is a highly concentrated base, which is very corrosive. I would assume, that its concentration is quite unstable.

It will, for example, quite rapidly react with carbon dioxide from the air:
$$\ce{NaOH + CO2 -> NaHCO3}\tag{1}$$

Also it will corrode glass containers, dissolving minerals like magnesium and calcium from it: $$\ce{Mg^{2+} + 2NaOH -> Mg(OH)2 v + 2Na+ }$$

A PE bottle should be used to avoid that.

Even if you worked in a very clean and low humidity environment, the surface of your pallets will be corroded since sodium hydroxide is hygroscopic and will further react according to $(1)$, even when stored carefully.

Therefore the concentration you obtain by weighing the pallets can only be quite approximate. If you need to know the exact concentration of your base, you have to calibrate it versus a primary standard, like dried succinic acid, before and after the intended use. In your case standardisation will indeed be not easy to perform, since your concentration is very high. Most likely there are uncertainties to the procedure that will likely leave you with similar error bars than not doing the calibration.

• I am in complete agreement with the answer above. I am just curious as to why you would need to know the exact concentration of such a very concentrated solution. However, If you do need to standardise it with any degree of accuracy, you will need to dilute it quantitively to match the concentration of the standard acid you are using in order that the volumes used match each other as closely as possible. – ed kinsella Dec 4 '14 at 8:59
• actually this is for my undergraduate research and since some of my friends asked me whether I have standardized it or not, I became curious about it (and be prepared if my examiners ask). I'm using it to make titania nanotube via alkaline hydrothermal method. thank you for of your answers, both of you :) – Inna Yusnila Khairani Dec 7 '14 at 8:41