How many grams of sodium hydroxide are there in 500 ml of 0.1 M solution?

Given:
V solution (NaOH) = 500 ml = 0.5 l
Cm (NaOH) = 0.1 M

To find:
m (NaOH) -?

Decision:
1) Calculate the amount of NaOH substance:
n (NaOH) = Cm (NaOH) * V solution (NaOH) = 0.1 * 0.5 = 0.05 mol;
2) Using the periodic system of D.I.Mendeleev, calculate the molar mass of NaOH:
M (NaOH) = Mr (NaOH) = Ar (Na) * N (Na) + Ar (O) * N (O) + Ar (H) * N (H) = 23 * 1 + 16 * 1 + 1 * 1 = 40 g / mol;
3) Calculate the mass of NaOH:
m (NaOH) = n (NaOH) * M (NaOH) = 0.05 * 40 = 2 g.

Answer: The mass of NaOH is 2 g.