Indicate how many moles 56 g of carbon monoxide contain.

Given:
m (CO) = 56 g

To find:
n (CO) -?

Decision:
1) Using the periodic system of D.I.Mendeleev, calculate the molar mass of carbon monoxide:
M (CO) = Mr (CO) = Ar (C) * N (C) + Ar (O) * N (O) = 12 * 1 + 16 * 1 = 28 g / mol;
2) Calculate the amount of carbon monoxide substance:
n (CO) = m (CO) / M (CO) = 56/28 = 2 mol.

Answer: The amount of carbon monoxide substance is 2 mol.