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Mole & Molar Mass, Study notes of Chemistry

Mole (mol): the amount of material counting 6.02214 × 1023 particles. The value of the mole is equal to the number of atoms in exactly 12 grams of pure.

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Mole & Molar Mass
Mole (mol): the amount of material counting 6.02214 × 1023 particles
The value of the mole is equal to the number of atoms in exactly 12 grams of pure
carbon-12.
12.00 g C-12 = 1 mol C-12 atoms = 6.022 × 1023 atoms
The number of particles in 1 mole is called Avogadro’s Number (6.0221421 x 1023).
6.022 ×1023atoms
1 mol or  1 mol
6.022 ×1023 atoms
Converting between Number of Moles and Number of Atoms
Calculate the number of atoms in 2.45
mol of copper.
A silver ring contains 1.1 x 1022 silver
atoms. How many moles of silver are in
the ring?
2.45 mol Cu × 6.022 ×1023 atoms
1 mol
= 1.48 × 1024 atoms Cu
1.1 ×1022 atoms Ag × 1 mol
6.022 ×1023 atoms
= 1.8 × 10-2 mol Ag
Molar Mass: the mass of 1 mol of atoms of an element
An element’s molar mass in g/mol is numerically equal to the element’s atomic mass in
amu.
1 mol C
12.01 g C or 12.01 g C
1mol C
Converting between Mass and Number of Moles Converting between Mass and Number of Atoms
Calculate the moles of carbon in 0.0265 g of
pencil lead. How many aluminum atoms are in a can
weighing 16.2 g?
0.0265 g C × 1 mol C
12.01 g C
= 2.21 × 10-3 mol C
16.2 g Al × 1 mol Al
26.98 g Al × 6.022 ×1023 atoms
1 mol
= 3.62 × 1023 atoms Al
Atoms
mol Cu
g Al mol Al atoms Al
mol Ag Atoms Ag
mol C g C
pf2

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Mole & Molar Mass

Mole (mol): the amount of material counting 6.02214 × 10 23 particles

The value of the mole is equal to the number of atoms in exactly 12 grams of pure carbon-12.  12.00 g C-12 = 1 mol C-12 atoms = 6.022 × 10 23 atoms  The number of particles in 1 mole is called Avogadro’s Number (6.0221421 x 10^23 ).

6.022 ×

23

atoms

1 mol

or

1 mol

6.022 ×

23

atoms

Converting between Number of Moles and Number of Atoms

Calculate the number of atoms in 2. mol of copper.

A silver ring contains 1.1 x 10^22 silver atoms. How many moles of silver are in the ring?

2.45 mol Cu ×

6.022 ×10 23 atoms 1 mol = 1.48 × 10^24 atoms Cu

1.1 ×10 22 atoms Ag ×

1 mol 6.022 ×10 23 atoms = 1.8 × 10-2^ mol Ag

Molar Mass: the mass of 1 mol of atoms of an element

An element’s molar mass in g/mol is numerically equal to the element’s atomic mass in amu.

1 mol C

12.01 g C

or

12.01 g C

1 mol C

Converting between Mass and Number of Moles Converting between Mass and Number of Atoms

Calculate the moles of carbon in 0.0265 g of pencil lead.

How many aluminum atoms are in a can weighing 16.2 g?

0.0265 g C ×

1 mol C 12.01 g C

= 2.21 × 10-3^ mol C

16.2 g Al ×

1 mol Al 26.98 g Al

×

6.022 ×10 23 atoms 1 mol

= 3.62 × 10^23 atoms Al

mol Cu Atoms

g Al mol Al atoms Al

Atoms Ag mol Ag

g C mol C

Practice Problems

  1. How many atoms are there in each of following?

(a) 3.75 moles of silver (b) 2.36 moles of xenon (c) 158 kg of phosphorus

  1. What is the amount, in moles, of each of the following?

(a) 449 g of potassium (b) 11.8 g of Ar

(c) 2.16 x 10 24 atoms of lead

  1. What is the mass of each of the following?

(a) 1.9 x 10

24 atoms of Pb (in g)

(b) 4.87 x 10

25 atoms of Zn (in kg) (c) 2.33 x 10 20 atoms of oxygen (in ng)

  1. How many molecules are in 2.50 moles of CO 2?
  2. Calculate the mass , in grams, of 0.433 mol of calcium nitrate.

Hint: Formula Weight of Ca(NO 3 ) 2 = (AW of Ca) + 2(AW of N) + 6 (AW of O)

  1. Calculate the number of H atoms in 0.350 mol of C 6 H 12 O (^6)

References: Tro, Chemistry: A Molecular Approach 2 nd^ ed., Pearson Brown/LeMay/Bursten, Chemistry: The Central Science, 12 th^ ed., Pearson

Answers

(a) 2.26 × 10 1. 24 silver atoms; (b) 1.42 × 10 24 xenon atoms (c) 3.07 × 10 27 phosphorus atoms

(a) 11.5 moles; (b) 0.295 moles Ar; (c) 3.59 moles 2.

(a) ) 6.5 × 10 3. 2 g; (b) 5.29 kg; (c) 6.19 × 10 6 ng

1.51 x 10 4. 24 H atoms 24 2.53 x 10 6.^2 ) 3 Ca(NO 71.1 g 5. atoms;

Gram Moles^ Formula^ units

(atoms, molecules, ions)

molar mass Avogadro’s number