Question

* 10 What is the mass in grams of a sample of Mg(CIO3)2 that contains 6.0 x 1020 atoms of oxygen? (A) 31717. grams (B) 3. 1529 x 1047 grams (C) 1. 1502 grams (D) 31. 299 grams 11 Name the compound Pb(NO3)4. (A) lead (II) nitrite (B) lead (II) nitrate (C) lead (IV) nitrate (D) lead (III) nitride 12 What is the mass % of carbon in (C2H SO)? (A) 7.74% (B) 60.0 % (C) 20.6% (D) 30.7% (E) 79.8 %

Answer 1

10)

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: A

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