Question

Explain how to prepare 100.00 ± 0.05 ml of NaOH 0.15 M from 92.06 ± 0.1 % pure NaOH pellets. Indicate how you would label the solution following NFPA color code. What are the absolute and relative uncertainties on the obtained concentration?

Answer 1

for 100 ml of 0.15 M NaOH solution,

grams of NaOH needed = 0.15 M x 40 g/mol x 0.1 L = 0.6 g

0.1% uncertainty in 92.06% pure NaOH

for 0.6 g we must take = 0.6 x 100/92.06 = 0.652 g NaOH

so we have to take (with absolute uncertainty) : 0.652 g +/- 0.0006 g pure NaOH and dissolve it in 100 +/- 0.05 ml water to get 0.15 M NaOH solution

With relative uncertainty : 0.652 +/- 0.001 g pure NaOG in 100 +/- 0.0005 ml of water to get 0.15 M NaOH solution

It is labelled as NFPA 704 white color stripe which are reactive towards glass, corrosive and have health hazard level 3, to be stored separately.