Calculate the mass of 0.2 mol of lithium hydroxide.

Answer: m (LiOH) = 4.8 g.
Explanation of the solution to the problem: to solve this problem, you must use the following formula:
m = n * M, where n is the amount of the substance (in this case, the amount of the lithium hydroxide substance is n (LiOH) = 0.2 mol); m is the mass of the substance, g; M is the molar mass of the substance (found from the periodic table of elements of D. I. Mendeleev), M (LiOH) = 7 + 16 + 1 = 24 g / mol.
Substituting the values known from the condition of the problem into the formula, we obtain:
m (LiOH) = n (LiOH) * M (LiOH) = 0.2 * 24 = 4.8 g.