Chemical Bonds, Water Properties, and Acid-Base Chemistry

These flashcards review key lecture ideas: ionic vs covalent bonds, electronegativity, hydrogen bonding, properties of water, surface tension, dissolution of salts, pH concepts, buffer systems, acid-base definitions, ketoacidosis, and electrolyte replacement.

What is an ionic bond?

A chemical bond formed when one atom permanently transfers an electron to another, creating oppositely charged ions that attract each other.

Why must ion formation occur when an ionic bond is created?

Because one atom ends up with too many electrons (negative ion) and the other with too few (positive ion), generating electrostatic attraction.

Why do ionic bonds weaken in the human body?

Water molecules insert between the ions; their polarity shields the charges and competes with the ionic attraction, making the bond easier to break.

What does electronegativity describe?

An atom’s tendency or desire to attract and hold onto electrons.

How does electronegativity determine bond type?

Equal pull → non-polar covalent; unequal but shared → polar covalent; extreme difference → ionic bond.

Why is NaCl a classic example of an ionic compound?

Sodium easily loses one electron, chlorine strongly attracts one electron; the transfer completes both outer shells and forms Na⁺ and Cl⁻.

Define a polar covalent bond.

A covalent bond in which electrons spend more time around the more electronegative atom, creating partial charges (δ+ / δ−).

What is hydrogen bonding?

A weak attraction between a hydrogen atom already covalently bonded to an electronegative atom (e.g., O, N) and a nearby electronegative atom on another molecule or part of the same molecule.

List two biologically important consequences of hydrogen bonding in water.

1) Cohesion and surface tension (water beads, belly-flop effect). 2) Water remaining liquid at room temperature by sticking to itself.

Why can you ‘belly-flop’ off a high dive and feel like you hit concrete?

Millions of hydrogen bonds at the water’s surface must break simultaneously, briefly making the surface very resistant to penetration.

How do hydrogen bonds stabilize DNA yet allow replication?

Individually weak so enzymes can unzip strands, but in huge numbers (≈4.5 billion per genome) they collectively hold the double helix together.

What is the Arrhenius definition of an acid and a base?

Acid: produces H⁺ in water. Base: produces OH⁻ in water.

Why does ammonia (NH₃) challenge the Arrhenius definition?

It acts as a base without containing OH⁻, so Arrhenius cannot explain its basicity.

State the Brønsted-Lowry definition of acids and bases.

Acid = proton (H⁺) donor; Base = proton (H⁺) acceptor.

What is meant when chemists say “a proton” in acid-base discussions?

A bare hydrogen nucleus (H⁺) with its electron removed; proton and H⁺ are identical terms.

Define pH in simple biochemical terms.

A logarithmic measure of hydrogen-ion concentration; acids raise [H⁺], bases lower [H⁺]/raise [OH⁻].

What is the narrow survivable blood-pH range for humans?

Approximately 7.35–7.45; falling to 7.3 or rising to 7.6 can be fatal.

How does the bicarbonate buffer system resist pH change?

Carbonic acid (H₂CO₃) donates H⁺ when solution becomes basic; bicarbonate (HCO₃⁻) accepts H⁺ when solution becomes acidic, shifting equilibrium to oppose pH change.

What is ketoacidosis and how does it disrupt buffering?

A dangerous drop in blood pH caused by accumulation of keto-acids during uncontrolled diabetes or prolonged protein catabolism, overwhelming the bicarbonate buffer.

Why was the sports drink ‘Gatorade’ invented?

Scientists found athletes lost not just water but electrolytes (ions) in sweat; replacing them improved performance and prevented dehydration imbalance.

Why is water called a ‘universal solvent’ for ionic compounds?

Its polar molecules surround and separate ions (hydration shells), overcoming ionic attractions and allowing salts to dissolve.

What property of identical atoms bonding together (e.g., O₂, N₂) keeps the molecule non-polar?

Equal electronegativity results in symmetric electron sharing, so no partial charges form.

How do partial charges form in a water molecule?

Oxygen’s high electronegativity pulls shared electrons toward itself, giving O a slight negative charge (δ−) and hydrogens slight positive charges (δ+).