Untitled Quiz

Study Notes

Water is slightly blue, but appears colorless in small quantities.
Water vapor is invisible.
Water is transparent to the visible light spectrum, allowing aquatic plants to photosynthesize.
Water absorbs ultraviolet and infrared light strongly.

Water is a dipole due to the difference in electronegativity between hydrogen and oxygen.
Oxygen is more electronegative than hydrogen.
Oxygen is sp3 hybridized with tetrahedral electron geometry and bent molecular geometry.

Hydrogen bonds are strong in water due to:
- The O—H bond's polarity.
- Two lone pairs on the oxygen atom.
- Each water molecule can form four hydrogen bonds to other molecules, resulting in a tetrahedral arrangement.

The concept of p[H] was introduced in 1909 and revised to pH in 1924.
The definition of 'p' in pH is unclear, but is often interpreted as "percentage".

Amphipathic compounds contain both hydrophobic (nonpolar) and hydrophilic (polar or ionic) groups.
They do not dissolve in water individually.
At a certain concentration, they form micelles:
- Micelles have hydrophilic groups on their exterior and hydrophobic groups clustered in their interior.
- Micelles are stabilized by hydrogen bonding with water, van der Waals forces between hydrocarbon groups, and hydrophobic interactions.

Osmotic pressure is the tendency of water molecules to migrate from a diluted solution to a concentrated solution through a semipermeable membrane.
This migration of water molecules is called osmosis.
A one-osmolal solution contains 1 mol of solute particles in 1 kg of water.

Monoprotic acids donate one proton per molecule during dissociation:
- HA(aq) + H2O(l) ⇌ H3O+(aq) + A−(aq)
Examples include hydrochloric acid (HCl) and nitric acid (HNO3).
Organic monoprotic acids often contain one carboxylic acid group.
Examples include formic acid (HCOOH), acetic acid(CH3COOH), and benzoic acid (C6H5COOH).

Polyprotic acids donate more than one proton per molecule.
Diprotic acids donate two protons:
- H2A(aq) + H2O(l) ⇌ H3O+(aq) + HA−(aq)
- HA−(aq) + H2O(l) ⇌ H3O+(aq) + A2−(aq)
Triprotic acids donate three protons.
Dissociation constants (Ka1 and Ka2) exist for each dissociation step.
Ka1 is typically greater than Ka2.
Examples include sulfuric acid (H2SO4) and carbonic acid (H2CO3).

Bases release hydroxide ions (OH−) in aqueous solutions.
They have slippery feel, bitter taste, change indicator colors, react with acids to form salts, promote certain chemical reactions (base catalysis), accept protons from proton donors, and contain completely or partially displaceable OH− ions.

This refers to the relationship between water and hydrophobic molecules (low water-soluble molecules).
Nonpolar substances tend to aggregate in aqueous solutions, excluding water molecules.
This is an entropy-driven process, as dissolving hydrophobic substances in water is thermodynamically unfavorable.
ΔG = ΔH – TΔS
Water molecules align themselves around non-polar molecules, losing freedom to form hydrogen bonds. - This entropy loss creates a thermodynamic barrier.
Multiple hydrophobic molecules aggregate, increasing the entropy of the system. - Fewer water molecules are needed to surround the aggregate.
Water-soluble compounds have stronger interactions between solute and water than between solute molecules. - Examples: salts, biological molecules with polar or ionic groups (e.g., glucose, ethanol).