When burning 6.2 g of siliceous hydrogen, 12 g of silicon oxide was obtained (4). The vapor density of the starting

When burning 6.2 g of siliceous hydrogen, 12 g of silicon oxide was obtained (4). The vapor density of the starting material in air is 2.14. Determine the molecular formula of silicon hydrogen.

Let’s find the number of silicon atoms in the oxide.

M (SiO2) = 60 g / mol.

60 g / mol SiO2 contains 28 g / mol Si.

12 g SiO2 contains x g Si.

60 g / mol – 28 g / mol,

12 g – x g

x = (12 × 28): 60 = 5.6 g.

Let us find the number of hydrogen atoms H.

6.2 g – 5.6 g = 0.6 g.

Let’s find the amount of matter of atoms.

n (Si) = 5.6: 28 g / mol = 0.2 mol.

n (H) = 0.6: 1 g / mol = 0.6 mol.

Let’s find the ratio of the amounts of substances.

Si: H = 0.2: 0.6 = 1: 4.

Let’s find the molar mass of silicon hydrogen.

M (air) = 29 g / mol.

D (air) = 29 g / mol × 2.14 = 62 g / mol.

Answer: Si2H6.