2 Hg (l) O2 (g) 2 HgO (s) exothermic

1
Given

• 2 Hg (l) O2 (g) 2 HgO (s)
  exothermic

?H increasing or decreasing? favorable or
unfav? ?S increasing or decreasing? favorable
or unfav? ?G increasing or decreasing?
favorable or unfav?
2
Given

• 2 Hg (l) O2 (g) 2 HgO (s) ?H
  -181 kJ

What is ?H for reaction of 2 moles of O2?
Calculate ?H for the reaction of 100.0 grams of
Hg.
3
Given

• 2 Hg (l) O2 (g) 2 HgO (s) ?H
  -181 kJ ?S -67 J/K

What is ?G at 50 C?
4
Calculate heat needed for 230 g ice 230 g
water at 0 C at 30 C
5
Chem 140 Chap 10 Gases, Liquids, Solids

• Gases have little or no interactions, expand to
  fill space
• Liquids have significant interactions, defined
  volume, no defined shape.
• Solids have defined volume and shape.

Gas Liquid Solid
Shape Volume Interactions
6
Comparison of Gases Liquids and Solids

• Gases have little or no interactions, expand to
  fill space
• Liquids have significant interactions, defined
  volume, no defined shape.
• Solids have defined volume and shape.

There are no forces (or very weak forces)
holding gas molecules together, so they tend to
fly apart. What holds liquid and solid molecules
together?
Gas Liquid Solid
7
Intermolecular Forces

• Liquid and solid molecules are held together by
  intermolecular forces based on polarity.
• Polar molecules have an end that is partially
  positive (?) and an end that is partially
  negative (?-).
• Since opposites attract, the partial positive on
  one molecule is attracted to the partial minus on
  a neighboring molecule.

8
Polar Molecules - Bonds

• What makes a molecule polar?

1) and 2)
Polar bonds based on a concept called
electronegativity, which is the ability of an
atom to pull on electrons of a covalent bond.
9
Electronegativity (EN or eleneg) 7.4

• Electronegativity the ability of an atom to
  attract electrons in a covalent bond.
• Examples Hydrogen (H2) and HCl
• HH or HH Atoms pulls equally on electrons
• HCl or HCl Cl pulls more strongly on the
  two electrons of the covalent bond.

10
Electronegativity Periodic Properties
Eleneg for elements on the periodic table show
clear trends.
11
Bond Polarity from Electronegativity

• To determine the polarity of a bond between two
  atoms, find the difference in electronegativity
  (EN)
• ?EN 0 to 0.4 bond is non-polar covalent
• ?EN .5 to 1.9 bond is polar covalent
• ?EN gt 2.0 bond in ionic

These electronegativity differences are rough
guidelines.
12
Bond Polarity from Electronegativity

• ?EN 0 to 0.4 bond is non-polar covalent
• ?EN .5 to 1.9 bond is polar covalent
• ?EN gt 2.0 bond in ionic

Find the difference in EN and classify the
following bonds C H Li O
P Cl
EN
?EN
13
Polar Molecules - Shapes

• What makes a molecule polar?

1) Polar Bonds and 2)
Unsymmetrical Shape
Shape of Molecules bases on the idea that
electrons want to spread out and stay far away
from each other. This theory is called Valence
Shell Electron Pair Repulsion or VSEPR.
14
VSEPR 7.9

• VSEPR based on the idea that atoms and lone
  pairs around a central atom will spread out as
  far as possible, due to the repulsion of the
  electron clouds.
• To determine geometry, count atoms lone pairs
  (charge clouds) around the central atom.

A t o m s L o n e P a i r s
2 3 4
Electron PairGeometry
15
EP Geometry and Shape of Molecules

• What is the electron pair geometry for the
  following molecules? (consider lone pairs AND
  atoms)
• What is the molecular shape? (consider only
  atoms)
• a. NH3 b. CF4 c. H2O
  d. SO2

atoms lone pairs
16
Dipole Moments 01

• Polar covalent bonds form between atoms of
  different electronegativity.
• A molecule has polar bonds that are unsymmetrical
  will be polar, and have a dipole moment.

17
Dipole Moments 03

• Polarity can be illustrated with an
  electrostatic potential map. These show
  electron-rich groups as red and electron-poor
  groups as blue-green.

18
Dipole Moments 04
These molecules are symmetrical, so dipole moment
is zero.
19
Dipole Moments 05

• Which of the following compounds will have a
  dipole moment? Show the direction of each.
• a. BH3 b. CF4 c. H2O d. SO2