Chemistry

Topics: Chemical reaction, Hydrogen, Chemistry Pages: 19 (2616 words) Published: August 23, 2013
Chapter 6 Chemical Reactions and Quantities
The Mole

General, Organic, and Biological Chemistry

Copyright © 2010 Pearson Education, Inc.

1

Collection Terms
A collection term states a specific number of items.
 1 dozen donuts

= 12 donuts

 1 ream of paper = 500 sheets  1 case = 24 cans

General, Organic, and Biological Chemistry

2

A Mole of Atoms
A mole is a collection that contains  the same number of particles as there are carbon atoms in 12.0 g of carbon 12C  6.02 x 1023 atoms of an element (Avogadro’s number) 1 mole of Element 1 mole of C = 1 mole of Na = 1 mole of Au = Number of Atoms 6.02 x 1023 C atoms 6.02 x 1023 Na atoms 6.02 x 1023 Au atoms

General, Organic, and Biological Chemistry

Copyright © 2010 Pearson Education, Inc.

3

A Mole of a Compound
A mole  of a covalent compound has Avogadro’s number of molecules 1 mole of CO2 = 6.02 x 1023 CO2 molecules 1 mole of H2O = 6.02 x 1023 H2O molecules  of an ionic compound contains Avogadro’s number of

formula units 1 mole of NaCl = 6.02 x 1023 NaCl formula units 1 mole of K2SO4 = 6.02 x 1023 K2SO4 formula units General, Organic, and Biological Chemistry Copyright © 2010 Pearson Education, Inc. 4

Avogadro’s Number
Define Avogadro's number, NA.


NA = 6.02 x 1023 particles/mole

Define the mole as


1 mole = 6.02 x 1023 atoms/molecules/ions

5

Using Avogadro’s Number
Avogadro’s number is used to convert moles of a substance to particles.

How many Cu atoms are in 0.50 mole of Cu? Rearrange formula Number of atoms = Number of moles x NA = 0.5 x 6.02 x 1023 Cu atoms = 3.0 x 1023 Cu atoms 6

Using Avogadro’s Number (continued)
Avogadro’s number is used to convert particles of a substance to moles. How many moles of CO2 are in 2.50 x 1024 molecules of CO2?

Number of moles =

2.5 x 1024 NA = 4.15 moles of CO2

General, Organic, and Biological Chemistry

Copyright © 2010 Pearson Education, Inc.

7

Subscripts and Moles
The subscripts in a formula give  the relationship of atoms in the formula  the moles of each element in 1 mole of a compound Glucose C6H12O6
In 1 molecule: 6 atoms of C 12 atoms of H 6 atoms of O In 1 mole: 6 moles of C 12 moles of H 6 moles of O

General, Organic, and Biological Chemistry

Copyright © 2010 Pearson Education, Inc.

8

Subscripts State Atoms and Moles

1 mole of C9H8O4 = 9 moles of C 8 moles of H 4 moles of O
General, Organic, and Biological Chemistry 9

Chemical Reactions and Quantities
Molar Mass

General, Organic, and Biological Chemistry

Copyright © 2010 Pearson Education, Inc.

10

Molar Mass
The molar mass is  the mass of one mole of a substance  the atomic mass of an element expressed in grams

General, Organic, and Biological Chemistry

Copyright © 2010 Pearson Education, Inc.

11

Molar Mass of CaCl2
 For a compound, the molar mass is the sum of the

molar masses of the elements in the formula. We calculate the molar mass of CaCl2 to the nearest 0.1 g as follows. Element Number of Moles Atomic Mass Total Mass

Ca

1

40.1 g/mole

40.1 g

Cl
CaCl2

2
1

35.5 g/mole

71.0 g
111.1 g

General, Organic, and Biological Chemistry

Copyright © 2010 Pearson Education, Inc.

12

Molar Mass of K3PO4
Determine the molar mass of K3PO4 to 0.1 g.
Element Number of Moles Atomic Mass Total Mass in K3PO4

K P

3 1

39.1 g/mole 31.0 g/mole

117.3 g 31.0 g

O
K3PO4

4
1

16.0 g/mole

64.0 g
212.3 g

General, Organic, and Biological Chemistry

Copyright © 2010 Pearson Education, Inc.

13

One-Mole Quantities

32.1 g

55.9 g

58.5 g

294.2 g

342.3 g

General, Organic, and Biological Chemistry

Copyright © 2010 Pearson Education, Inc.

14

Guide to Calculating Molar Mass

General, Organic, and Biological Chemistry

15

Moles and the molar mass

Example: Aluminium is often used for the structure of bicycle frames. How many grams are in...
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