To vaporize 100. grams of water at 100.°C to steam at 100.°C:
Use: m × heat of vaporization = qTotal heat = 33.44 kJ + 41.8 kJ + 225.72 kJ = 300.96 kJWater’s Reactions with Anhydrides
Anhydrides are certain oxides that react with water to form two classes of
compounds—acids and bases.
Many metal oxides react with water to form bases such as sodium hydroxide,
potassium hydroxide, and calcium hydroxide. For this reason, they are called
basic anhydrides or basic oxides. The common bases are water solutions that
contain the hydroxyl (OH−) ion. Some common examples are:
In general then: Metal oxide + H 2 O → Metal hydroxide
In a similar manner, nonmetallic oxides react with water to form an acid
such as sulfuric acid, carbonic acid, or phosphoric acid. For this reason, they are
referred to as acidic oxides or acidic anhydrides. (The term acid anhydride is
now used to refer to specific organic compounds.) The common acids are water
solutions containing hydrogen ions (H+). Some common examples are:
In general, then: Nonmetallic oxide + H 2 O → AcidPOLARITY AND HYDROGEN BONDING
Water is different from most liquids in that it reaches its greatest density at 4°C
and then its volume begins to expand. By the time water freezes at 0°C, its volume
has expanded by about 9 percent. Most other liquids contract as they cool and
change state to a solid because their molecules have less energy, move more
slowly, and are closer together. This abnormal behavior of water can be
explained as follows. X-ray studies of ice crystals show that H 2 O molecules are