Question

Calculate the mass (in  g) of each sample.

6.31×10²⁰ SO3 molecules​

2.4×10²² H2O molecules​

4.6×10²⁵ O3 molecules​

9.85×10¹⁹ CCl2F2 molecules​

Answer 1

1)

use:

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

number of mol = 6.31*10^20 / 6.022*10^23 mol

number of mol = 1.048*10^-3 mol

Molar mass of SO3,

MM = 1*MM(S) + 3*MM(O)

= 1*32.07 + 3*16.0

= 80.07 g/mol

use:

mass of SO3,

m = number of mol * molar mass

= 1.048*10^-3 mol * 80.07 g/mol

= 8.39*10^-2 g

Answer: 8.39*10^-2 g

2)

use:

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

number of mol = 2.4*10^22 / 6.022*10^23 mol

number of mol = 3.985*10^-2 mol

Molar mass of H2O,

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

= 2*1.008 + 1*16.0

= 18.016 g/mol

use:

mass of H2O,

m = number of mol * molar mass

= 3.985*10^-2 mol * 18.02 g/mol

= 0.718 g

Answer: 0.718 g

3)

use:

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

number of mol = 4.6*10^25 / 6.022*10^23 mol

number of mol = 76.39 mol

Molar mass of O2 = 32 g/mol

use:

mass of O2,

m = number of mol * molar mass

= 76.39 mol * 32 g/mol

= 2.4*10^3 g

Answer: 2.4*10^3 g

4)

use:

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

number of mol = 9.85*10^19 / 6.022*10^23 mol

number of mol = 1.636*10^-4 mol

Molar mass of CCl2F2,

MM = 1*MM(C) + 2*MM(Cl) + 2*MM(F)

= 1*12.01 + 2*35.45 + 2*19.0

= 120.91 g/mol

use:

mass of CCl2F2,

m = number of mol * molar mass

= 1.636*10^-4 mol * 1.209*10^2 g/mol

= 1.978*10^-2 g

Answer: 1.98*10^-2 g