1. LESSON TOPIC: The Inorganic Chemistry of Water

2. What is salinity? What are the major sea salts?
Salinity- the total quantity or concentration of all dissolved inorganic solids, or more precisely, ions.
This is the sodium chloride and everything else, commonly called the dissolved salts.

3. Salinity is expressed in parts per thousand .
The abbreviation ‰ stands for “parts per thousand”
The ocean’s average salinity is 35‰.
The most common salts:
sodium chloride (NaCl)
potassium chloride (KCl).

5. What are the colligative properties of seawater
What are the colligative properties of seawater? Does fresh water have these properties?
The properties of a liquid that may be altered by the presence of a solute are called colligative properties.

6. Raised boiling point.
Decreased freezing temperature.
Ability to create osmotic pressure.
Electrically conductive.
Decreased heat capacity.
Slowed evaporation.

7. What are the most abundant chemicals in seawater?
Let’s suppose you have one kilogram of seawater with average salinity (35‰). This means that 3.5%, or 35 grams, would be dissolved solids. Based on constant proportions, this would break down to these approximate numbers:
Cl-) Chloride g
(Na+) Sodium g
(SO42-) Sulfate 2.65 g
(Mg2+) Magnesium 1.28 g
(HCO3) Bicarbonate 0.14 g
(Ca2+) Calcium 0.40 g
(K+) Potassium 0.38 g
Other 0.61 g

8. How do marine scientists determine salinity?
Salinity is determined with a salinometer, which determines the electrical conductivity of the water.
(CTD) sensors
Thermistor - temperature.
Conductivity - current flowing between two platinum electrodes sealed in a tube of non-conducting glass.
Pressure measurements are made by measuring the natural frequency of a quartz crystal.

13. How do temperature and salinity affect seawater density?
Salinity and temperature also vary with depth.
Density differences cause water to separate into layers. High-density water lies beneath low-density water.
Low temperature and high salinity are features of high-density water.

14. What factors affect seawater’s pH? Why does pH change with depth?
Pure water has a pH of 7, which is neutral.
Seawater pH typically ranges from 7.8 to 8.3, which is very mildly alkaline.
However, the ocean’s pH remains relatively stable due to buffering.
A buffer is a substance that reduces the tendency of a solution to become too acidic or too alkaline.