Chemistry
Water, Acids and Bases
Inorganic Chemistry

The study of inorganic compounds



water
acids
bases
Water

Chemical formula = H2O

Properties



Cohesive, form H bonds
Adhesive, clings to surfaces
Polar
Cohesion and Adhesion

among water molecules
plays a key role in the
transport of water against
gravity in plants
sequoias
wood cut

clinging of one substance to
another, contributes too, as
water adheres to the wall of
the vessels.
Surface Tension

a measure of the force necessary to stretch or break the
surface of a liquid, is related to cohesion.



Water has a greater surface tension than most other
liquids
Water behaves as if
covered by an invisible
film
Some animals can stand,
walk, or run on water
without breaking the
surface
Polarity of Water


The molecule has opposite charges on opposite
sides
polar molecules form H bonds with other polar
molecules
Activity

Explain why water sticks to your
skin when you take your finger out
of the water.

Explain why these leaves float
instead of submerging.

Name the property that makes
water molecules attach to each
other due to its surface charge.
answers
Adhesion & cohesion
Surface tension
Polarity
Water is the Solvent of Life

solution = solvent + solute(s)

ex: cup of coffee




hot water (solvent)
sugar (solute)
coffee grounds (solute)
Aqueous solution

The solvent is water
ramsey.k12.nj.us
Water Forms Hydrogen Bonds With Ions



The Na+ cations form hydrogen bonds with partial
negative oxygen regions of water molecules.
The Cl- anions form
hydrogen bonds with
the partial positive
hydrogen regions of
water molecules.
Hydration shell - each
dissolved ion is surrounded
by a sphere of water
molecules


Polar molecules are also soluble in water.
Even large molecules, like proteins, can dissolve
in water if they have ionic and polar regions.
Hydrophilic

any substance that has an affinity for water



Some are water-soluble
water molecules are attracted to molecules with an
electrical charge (ionic or polar bonds)
H-bond formation may form
Hydrophobic

Substances that have no affinity for water




Non-ionic & non-polar compounds are repelled by
water
Water-insoluble
Hydrophobic molecules are major ingredients of
cell membranes
Some vegetables and fruits with non-polar
pesticides
Mole concept

Counting individual or even collections of
molecules is not practical

Instead, we can use the concept of a mole to
convert weight of a substance to the number of
molecules in that substance and vice versa
Mole (mol)

Is equal in number to the molecular weight of a
substance, but up scaled from daltons to grams

Ex. a mole of sucrose (C12H22O11)





C = 12 daltons x 12
H = 1 dalton x 22
O = 16 daltons x 11
Sucrose molecular weight = 342 daltons
one mole of sucrose = 342 g
Avogradro’s number

The actual number of molecules in a mole
6.023 x 1023

A mole of sucrose


contains 6.023 x 1023 molecules
weighs 342g
Molarity

the concentration of a material in solution

one molar solution

has one mole of a substance dissolved in one liter of solvent,
typically water.

Example: to make a 1 molar (1 M) solution of sucrose add
water to 342 g of sucrose until the total volume is 1
liter and all the sugar is dissolved
Ionization of Water

2 H2O
+
H3O+
+
OH-
-
+
hydronium
hydroxide
H+
+ OH-

by convention: H2O

pH of pure water is 7 (10-7 M)
pH

Scale 0-14
 logarithmic scale

pH = - log10 [H+]




acid pH< 7
base pH>7
neutral pH = 7
pure water at RT:
pH = -log 10-7M
= -(-7) = 7
Neutral Solution




In a neutral solution [H+] = [OH-] = 10-7 M, and the
pH = 7.
Values for pH decline as [H+] increase.
While the pH scale is based on [H+], values for [OH-]
can be easily calculated from the product
relationship
[H+] + [OH-] = 14
Acids

substances that increase [H+] in solution

pH below 7



ex: HCl
H+ + Cl acid precipitation, with pH < 5
acid indigestion use antacids
Bases

substances that reduce [H+] in solution

pH above 7

NH3 + H+
NH4 +
ammonia

NaOH
sodium hydroxide
ammonium ion
Na+ + OHsodium
ion
hydroxyde
ion
Activity

Rain has a pH of 5.



Is it an acid, base or neutral?
What is the concentration of H ions?
What is the concentration of OH ions?
answers

Rain has a pH of 5.



acid
[H+] = 10-5 M
[OH-] = 10-9 M
Buffer



prevents sudden pH changes in biological fluids
accept hydrogen ions from the solution when
they are in excess and donate hydrogen ions
when they have been depleted
H2CO3
HCO3-
carbonic acid
(donor of H+)
bicarbonate ion
(receptor of H+)
The End
+
H+
hydrogen
(ion)