Page 15 - Pharmaceutical_Analytical_Chemistry_1_Theoretical_Notes_Level_1

Mansoura National University
Pharm D-Clinical Pharmacy Program Level 1 Pharm. Anal. Chem. 1 (PC 101)

Example 2

How many atoms are present in 17 moles of water?تارذلا عون ددحا مل

In order to convert moles of a substance to atoms one must first convert moles to

molecules
Step 1 : moles molecules
23
1 mole H O = 6.022 X 10 molecules
2
23 25
17 moles H O contains: 17 x 6.022 X 10 molecules = 1.02 X 10 molecules H O
2 2
Step 2: molecules atoms
N.B. this depends upon the formula of the substance which in this case is H O.
2
According to the formula for H O:
2
1 molecule H O = 2 atoms H + 1 atom O = 3 atoms total
2
1 molecule H O 3 atoms
2
25
1.02 X 10 molecule X atoms
25 25
X=(3 x 1.02 X 10 )/1 = 3.06 X 10 atoms H O
2

Quiz

1. How many grams are in 1.2 moles of neon? (Ne: 20)

23
a) 0.059 g b) 7.2 x 10 g
c) 2.0 x 10 -24 g d) 24 g

2. How many moles are in 6.02 x 10 molecules of H2O?
23
a) 1 mole b) 2 moles

c) 6.02 moles d) 602000000 moles

3. The 3 moles of carbon will have -------- Avogadro no. of particles.

10