1. Solutions

advertisement
General, Organic, and
Biological Chemistry
Fourth Edition
Karen Timberlake
Chapter 8
Solutions
8.1
Solutions
© 2013 Pearson Education, Inc.
Lectures
Solutions: Solute and Solvent
Solutions
 are homogeneous
mixtures of two or more
substances.
 contain a solute that is
uniformly dispersed in
another substance
called the solvent.
© 2013 Pearson Education, Inc.
Chapter 8, Section 1
2
Nature of Solutes in Solutions
Solutes
 are spread uniformly
throughout the solvent.
 are not visible, but can
give a color to the
solution.
 are usually present in a
smaller amount than
the solvent.
© 2013 Pearson Education, Inc.
Chapter 8, Section 1
3
Examples of Solutions
The solute and solvent in a solution can be a solid, liquid,
and/or a gas.
© 2013 Pearson Education, Inc.
Chapter 8, Section 1
4
Learning Check
Identify the solute in each of the following solutions.
1. 2 g sugar and 100 mL water
2. 60.0 mL of ethyl alcohol and 30.0 mL of
methyl alcohol
3. 55.0 mL water and 1.50 g NaCl
4. air: 200 mL O2 and 800 mL N2
© 2013 Pearson Education, Inc.
Chapter 8, Section 1
5
Solution
Identify the solute in each of the following solutions.
Solute
1. 2 g sugar and 100 mL water
sugar
2. 60.0 mL of ethyl alcohol and
30.0 mL of methyl alcohol
methyl alcohol
3. 55.0 mL water and 1.50 g NaCl
NaCl
4. air: 200 mL O2 and 800 mL N2
O2
© 2013 Pearson Education, Inc.
Chapter 8, Section 1
6
Water
Water
 is the most common solvent in nature.
 is a polar molecule.
 forms hydrogen bonds between the partially positive
hydrogen atom in one molecule and the partially
negatively charged oxygen atom in a different water
molecule.
© 2013 Pearson Education, Inc.
Chapter 8, Section 1
7
Water in the body
 The average adult body contains 60% water by
mass.
 Dehydration occurs when as little as 10% of body
fluids are lost.
 Water lost can be replaced by liquids and foods in
the diet.
© 2013 Pearson Education, Inc.
Chapter 8, Section 1
8
Formation of a Solution
 To form a solution, the solute and solvent must
have like polarities.
 The energy between the solute and solvent
particles must be strong enough to overcome the
initial attractive forces between the solvent
molecules and solute particles.
© 2013 Pearson Education, Inc.
Chapter 8, Section 1
9
Solutions with Ionic and Polar
Solutes
Na+ and Cl– ions
 on the surface of a NaCl
crystal are attracted to
polar water molecules.
 are hydrated in solution by
many H2O molecules
surrounding each ion.
© 2013 Pearson Education, Inc.
Chapter 8, Section 1
10
Equations for Solution Formation
When NaCl(s) dissolves in water, the reaction can be
written as:
© 2013 Pearson Education, Inc.
Chapter 8, Section 1
11
Learning Check
Solid LiCl dissolves in water because:
A. The Li+ ions are attracted to the oxygen atom () of
water.
B. The Li+ ions are attracted to the hydrogen atom
( +) of water.
C. The Cl– ions are attracted to the oxygen atom ()
of water.
D. The Cl– ions are attracted to the hydrogen atom
( +) of water.
E. both A and D
F. both B and C
© 2013 Pearson Education, Inc.
Chapter 8, Section 1
12
Solution
Solid LiCl dissolves in water because:
A. The Li+ ions are attracted to the oxygen atom () of
water.
D. The Cl– ions are attracted to the hydrogen atom
( +) of water.
E. both A and D
© 2013 Pearson Education, Inc.
Chapter 8, Section 1
13
Water and a Polar Solute
Molecules of polar covalent compound methanol, CH3OH,
form hydrogen bonds with polar water molecules to form a
methanol–water solution.
© 2013 Pearson Education, Inc.
Chapter 8, Section 1
14
Like Dissolves Like
Two substances form a solution when
 there is an attraction between the particles of the
solute and solvent.
 a polar solvent, such as water, dissolves polar
solutes, such as sugar and/or ionic solutes, such
as NaCl.
 a nonpolar solvent, such as hexane (C6H14)
dissolves nonpolar solutes, such as oil or grease.
© 2013 Pearson Education, Inc.
Chapter 8, Section 1
15
Like Dissolves Like
Solvents
Solutes
Water (polar)
CH2Cl2 (nonpolar)
Ni(NO3)2
(polar)
I2 (nonpolar)
© 2013 Pearson Education, Inc.
Chapter 8, Section 1
16
Learning Check
Will each of the following solutes dissolve in water? Why
or why not?
A.
B.
C.
D.
Na2SO4
gasoline (nonpolar)
I2
HCl
© 2013 Pearson Education, Inc.
Chapter 8, Section 1
17
Solution
Will each of the following solutes dissolve in water? Why
or why not?
A.
B.
C.
D.
Na2SO4
gasoline
I2
HCl
Yes, the solute is ionic.
No, the solute is nonpolar.
No, the solute is nonpolar.
Yes, the solute is polar.
Most polar and ionic solutes dissolve in water because
water is a polar solvent.
© 2013 Pearson Education, Inc.
Chapter 8, Section 1
18
Download