What is the mass of 20 cm3 of a 10% NaOH solution?

Given:
V solution (NaOH) = 20 cm3 = 20 ml
ω (NaOH) = 10%

Find:
m (NaOH) -?

Solution:
1) Using special tables, determine the density of sodium hydroxide by the known mass fraction of the substance:
ρ solution (NaOH) = 1.1089 g / ml;
2) Calculate the mass of the sodium hydroxide solution:
m solution (NaOH) = ρ solution (NaOH) * V solution (NaOH) = 1.1089 * 20 = 22.178 g;
3) Calculate the mass of sodium hydroxide:
m (NaOH) = ω (NaOH) * m solution (NaOH) / 100% = 10% * 22.178 / 100% = 2.2178 g.

Answer: The mass of NaOH is 2.2178 g.