H2O is the chemical formula for water. Its common name is water and its IUPAC name is oxidane. Water has a molecular mass of 18 g/mol and is the most abundant compound on Earth's surface. It is essential for all known forms of life.
H2O is the chemical formula for water; IUPAC name is oxidane.
Molecular mass of H2O = 18 g/mol (2×1 + 16).
Water is a polar molecule with a bent geometry and bond angle of ~104.5°.
Boiling point: 100°C; Freezing point: 0°C at standard atmospheric pressure.
Water has maximum density at 4°C (~1 g/cm³).
Water is a neutral substance with pH = 7.
Hydrogen bonding between water molecules gives it a high specific heat capacity (4.18 J/g·°C).
Electrolysis of water: 2H2O → 2H2 + O2.
The chemical formula H2O tells us that each molecule of water contains two hydrogen atoms bonded to one oxygen atom. The IUPAC (International Union of Pure and Applied Chemistry) name for H2O is oxidane. In everyday language it is universally called water. The formula was established in the early 19th century and confirmed by the work of chemists such as Henry Cavendish and Antoine Lavoisier.
The molecular mass of H2O is calculated by adding the atomic masses of all atoms in the formula:
H2O: 2 × H + 1 × O = 2 × 1 + 1 × 16 = 2 + 16 = 18 g/mol
Atomic masses used: Hydrogen (H) = 1 g/mol, Oxygen (O) = 16 g/mol. Therefore the molar mass of water is 18 g/mol.
Key properties of water (H2O):
Water is a polar molecule due to the bent geometry (bond angle ~104.5°) and the electronegativity difference between oxygen and hydrogen. This polarity makes water an excellent solvent, often called the universal solvent.
In a water molecule, oxygen forms two covalent bonds with two hydrogen atoms. Oxygen also has two lone pairs of electrons, giving the molecule a bent (V-shaped) geometry. The bond angle H-O-H is approximately 104.5°. The partial negative charge on oxygen and partial positive charges on hydrogen atoms allow water molecules to form hydrogen bonds with each other. Hydrogen bonding accounts for water's unusually high boiling point, surface tension, and specific heat capacity compared to other molecules of similar size.
Water is indispensable in chemistry, biology, and daily life:
The common chemical name of H2O is water. Its IUPAC name is oxidane.
The molecular mass of H2O is 18 g/mol. It is calculated as 2 × 1 (H) + 1 × 16 (O) = 18 g/mol.
Water is called the universal solvent because its polarity allows it to dissolve a wide range of ionic and polar substances. The partial charges on the water molecule interact with charged ions and polar molecules, surrounding and dissolving them.
The H-O-H bond angle in a water molecule is approximately 104.5°. The molecule adopts a bent (V-shaped) geometry due to the two lone pairs of electrons on the oxygen atom.
When water undergoes electrolysis, it decomposes into hydrogen gas at the cathode and oxygen gas at the anode: 2H2O → 2H2 + O2.
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