Question

Glass is silicone dioxide (SiO₂). If a glass bottle contains 7.51x10²² molecules of SiO₂, SiO₂ mw: 60.08g/mol

A) What is the mass of the glass bottle?

B) How many grams of oxygen are present?

Answer 1

A)

use:

number of mol = number of molecules / Avogadro’s number

number of mol = 7.51*10^22 / 6.022*10^23 mol

number of mol = 0.1247 mol

Molar mass of SiO2,

MM = 1*MM(Si) + 2*MM(O)

= 1*28.09 + 2*16.0

= 60.09 g/mol

use:

mass of SiO2,

m = number of mol * molar mass

= 0.1247 mol * 60.09 g/mol

= 7.494 g

Answer: 7.49 g

B)

one mole of SiO2 contains 2 mole of O

use:

number of moles of O = 2 * number of moles of SiO2

= 2 * 0.1247

= 0.2494

Molar mass of O = 16 g/mol

use:

mass of O,

m = number of mol * molar mass

= 0.2494 mol * 16 g/mol

= 3.991 g

Answer: 3.99 g