Question

(D) nitrogen oxide 28 What is the mass in grams of a sample of Mg(ClO3)2 that contains 6.0 x 1026 atoms of oxygen? (A) 31. 299 grams (B) 1. 1502 grams (C)31717. grams (D) 3. 1529 x 10"7 grams

Answer 1

1 moles of Mg(ClO3)2 has 6 atoms of oxygen.
So, number of Mg(ClO3)2 = number of O / 6
= (6.0*10^26) / 6
= 1.0*10^26

use:
number of mol = number of molecules / Avogadro’s number
number of mol = 1*10^26 / 6.022*10^23 mol
number of mol = 1.661*10^2 mol

Molar mass of Mg(ClO3)2,
MM = 1*MM(Mg) + 2*MM(Cl) + 6*MM(O)
= 1*24.31 + 2*35.45 + 6*16.0
= 191.21 g/mol

use:
mass of Mg(ClO3)2,
m = number of mol * molar mass
= 1.661*10^2 mol * 1.912*10^2 g/mol
= 3.175*10^4 g
Answer: C