Properties of water, acids, bases and buffers

Vocabulary flashcards covering key terms from the lecture notes on water, acids, bases and buffers.

Ionic bond

Electrostatic attraction between oppositely charged ions, typically formed between a metal cation and a nonmetal anion.

Covalent bond

Sharing of electrons between atoms, forming a molecule.

Molecule

A group of two or more atoms held together by covalent bonds.

Ion

A charged particle formed when electrons are gained or lost.

Van der Waals forces

Weak intermolecular forces arising from temporary dipoles; include London dispersion and dipole-dipole interactions.

Hydrogen bond

A strong dipole-dipole interaction where a hydrogen atom bonded to N, O, or F interacts with a lone pair on another electronegative atom.

Polar bond

A covalent bond with unequal sharing of electrons due to differing electronegativities, producing partial charges.

Polar molecule

A molecule with regions of partial positive and partial negative charges due to polar bonds.

Partial charges

Small, non-integer charges (δ+ and δ−) on atoms within polar bonds.

Non-polar covalent bond

Covalent bond with equal sharing of electrons between atoms of similar electronegativity.

Electronegativity

Tendency of an atom to attract electrons in a bond.

Dipole

A separation of charge within a molecule resulting in partial positive and negative ends.

Cohesion

Attraction between like molecules (e.g., water–water).

Adhesion

Attraction between unlike molecules (e.g., water–surface).

Surface tension

The cohesive force at a liquid’s surface that makes it resist external penetration.

Polarity of water

Water has partial negative charge on oxygen and partial positive charges on hydrogens due to electronegativity differences.

Solvent

The dissolving agent in a solution.

Solute

The substance dissolved in a solvent.

Solution

A homogeneous mixture of two or more substances.

Aqueous solution

A solution in which water is the solvent.

Acid

Substance that donates H+ (protons) in water, increasing H+ concentration.

Base

Substance that accepts H+; Arrhenius bases release OH− when dissolved in water.

Hydronium ion

H3O+; the hydrated proton in water.

Hydroxide ion

OH−; conjugate base of water.

Arrhenius acid

Substance that increases H+ in solution by dissociating into H+ and negative ions.

Arrhenius base

Substance that increases OH− in solution by dissociating into cations and OH−.

Bronsted-Lowry acid

Species that donates a proton (H+) to another species.

Bronsted-Lowry base

Species that accepts a proton (H+).

Conjugate acid

Species formed when a base accepts a proton.

Conjugate base

Species formed when an acid donates a proton.

Equilibrium

State where forward and reverse reaction rates are equal and concentrations remain constant.

Keq

Equilibrium constant; ratio of product concentrations to reactant concentrations at equilibrium.

Kw (ion product of water)

Product [H+][OH−] of water; Kw = 1.0 × 10−14 at 25°C.

pH

Negative logarithm of the hydrogen ion concentration; a measure of acidity.

pKa

Negative logarithm of the acid dissociation constant Ka; pH at which a weak acid is half dissociated.

Henderson-Hasselbalch equation

Relationship: pH = pKa + log([A−]/[HA]), connects pH to conjugate base/acid ratio.

Buffer

A system (weak acid and conjugate base, or weak base and conjugate acid) that resists pH changes.

Buffering around pKa

A weak acid/base buffers most effectively near its pKa, resisting pH changes.