What is the amount of methane substance weighing 1.6 grams?

Given:
m (CH4) = 1.6 g

Find:
n (CH4) -?

Solution:
1) Using the periodic system of D.I.Mendeleev, calculate the molar mass of methane:
M (CH4) = Mr (CH4) = Ar (C) * N (C) + Ar (H) * N (H) = 12 * 1 + 1 * 4 = 16 g / mol;
2) Calculate the amount of methane substance:
n (CH4) = m (CH4) / M (CH4) = 1.6 / 16 = 0.1 mol.

Answer: The amount of CH4 substance is 0.1 mol.