H2O

Definition

H2O, or water, is a chemical compound consisting of two hydrogen atoms covalently bonded to a single oxygen atom. It is a colorless, odorless, and tasteless liquid that is essential for life on Earth, playing crucial roles in various chemical and physical processes across multiple topics in chemistry.

5 Must Know Facts For Your Next Test

1. H2O is the chemical formula for water, a vital compound for life on Earth that covers approximately 71% of the planet's surface.
2. Water exists in three main phases: solid (ice), liquid, and gas (water vapor), and can transition between these phases through various physical processes.
3. The molar mass of H2O is 18.02 g/mol, making it an important consideration in calculations involving formula mass and the mole concept.
4. Water is the primary solvent in many chemical reactions, and its concentration in solutions is often expressed as molarity (moles of solute per liter of solution).
5. The polarity of the H2O molecule, due to the unequal sharing of electrons, is responsible for its ability to participate in hydrogen bonding, which influences many of its physical and chemical properties.

Review Questions

• Explain how the phases and classification of matter relate to the properties of H2O.
  • The H2O molecule can exist in three main phases: solid (ice), liquid (water), and gas (water vapor). These phase changes are driven by the intermolecular forces, such as hydrogen bonding, that exist between H2O molecules. The ability of H2O to transition between these phases is a key characteristic that influences its classification as a pure substance and its behavior in various chemical and physical processes.
• Describe how the molar mass and mole concept of H2O are used in calculations involving formula mass and molarity.
  • The molar mass of H2O, 18.02 g/mol, is an important factor in calculations involving formula mass and the mole concept. The mole is a fundamental unit in chemistry that represents the amount of a substance, and the molar mass of H2O allows for the conversion between mass, moles, and the number of particles (molecules) of water. Additionally, the molar mass of H2O is a crucial component in determining the molarity of aqueous solutions, which is the concentration of a solute (such as H2O) in a solvent, expressed as moles of solute per liter of solution.
• Analyze how the polarity and hydrogen bonding of the H2O molecule influence its molecular structure and the hydrolysis of salts.
  • The polarity of the H2O molecule, with its slightly positive hydrogen atoms and slightly negative oxygen atom, allows for the formation of hydrogen bonds between water molecules. This hydrogen bonding network contributes to the unique physical and chemical properties of water, including its high boiling point, surface tension, and ability to act as both a proton donor and acceptor. The polarity and hydrogen bonding of H2O also play a crucial role in the hydrolysis of salts, where the water molecules can dissociate the ionic bonds, leading to the formation of new products through acid-base reactions.

Related terms

Polarity:

The unequal sharing of electrons between atoms in a molecule, resulting in a molecule having a slightly positive and slightly negative end.

Hydrogen Bonding:

A type of dipole-dipole attraction that occurs between a hydrogen atom covalently bonded to a highly electronegative atom, such as oxygen, and another nearby highly electronegative atom.

Hydrolysis:

A chemical reaction where a compound is broken down by the addition of water, typically resulting in the formation of new products.