Question

QUESTION 6 Which of the following has the greatest number of atoms? A. 1.0 mol He B.0.60 mol H2 C.20 g potassium D.8.5 mL H20 (Density of H20 = 1 g/mL) E 22.6 g KMnO4

Answer 1

A)

1.0 mol of He has 1.0 mol of atoms

B)

0.60 mol of H2 has 2*0.60 = 1.2 mol of atoms

C)

Molar mass of K = 39.1 g/mol

mass(K)= 20 g

use:

number of mol of K,

n = mass of K/molar mass of K

=(20 g)/(39.1 g/mol)

= 0.512 mol

So, this has 0.512 mol of K

D)

8.5 mL of H2O is 8.5 g of H2O

Molar mass of H2O,

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

= 2*1.008 + 1*16.0

= 18.016 g/mol

mass(H2O)= 8.5 g

use:

number of mol of H2O,

n = mass of H2O/molar mass of H2O

=(8.5 g)/(18.02 g/mol)

= 0.4718 mol

Count of each element in compound is:

{H=2, O=1}

Total mol of atoms in 1 mol of molecule = 3

use:

number of moles of atoms = number of moles of molecules * Total number of atoms in 1 molecule

number of moles of atoms = 0.4718 * 3

number of moles of atoms = 1.42 moles Atoms

E)

Molar mass of KMnO4,

MM = 1*MM(K) + 1*MM(Mn) + 4*MM(O)

= 1*39.1 + 1*54.94 + 4*16.0

= 158.04 g/mol

mass(KMnO4)= 22.6 g

use:

number of mol of KMnO4,

n = mass of KMnO4/molar mass of KMnO4

=(22.6 g)/(1.58*10^2 g/mol)

= 0.143 mol

Count of each element in compound is:

{K=1, Mn=1, O=4}

Total mol of atoms in 1 mol of molecule = 6

use:

number of moles of atoms = number of moles of molecules * Total number of atoms in 1 molecule

number of moles of atoms = 0.143 * 6

number of moles of atoms = 0.858 moles Atoms

Clearly number of atom is largest in case of D

Answer: D