Water, Acids & Bases, and Reactions (Notes Review)

Flashcards covering water properties, acids and bases, pH, buffers, solutions, electrolytes, mixtures, and basic hydrolysis/condensation concepts.

What makes a water molecule polar?

Oxygen is highly electronegative and holds a partial negative charge while hydrogen carries a partial positive charge, creating overall polarity.

How many hydrogen bonds can a water molecule form?

Up to four hydrogen bonds.

What are the partial charges on oxygen and hydrogen in H2O?

Oxygen is partially negative; hydrogen is partially positive.

Which substances dissolve readily in water and why?

Hydrophilic substances (polar or ionic) dissolve because water’s polarity enables favorable interactions; hydrophobic substances do not dissolve well.

What are cohesive and adhesive forces in water?

Cohesion is the attraction between water molecules; adhesion is the attraction between water molecules and other substances.

What provides water’s surface tension?

Hydrogen bonds between water molecules provide surface tension.

What is capillary action?

The movement of water against gravity due to cohesive and adhesive forces (e.g., in trees).

Why does water help regulate temperature in organisms and ecosystems?

Because water has a high specific heat and a high heat of vaporization due to hydrogen bonding.

What is the approximate energy required to convert 1 g of water to steam?

About 540 calories per gram.

Why does ice float on water?

Ice is less dense than liquid water, so it floats, which helps insulate bodies of water.

What is the principal solvent in living things?

Water.

What does the saying 'like dissolves like' mean in relation to water?

Polar (water-loving) substances dissolve in water; nonpolar substances do not dissolve well.

What is a Bronsted-Lowry acid?

A substance that donates a proton (H+).

What is a Bronsted-Lowry base?

A substance that accepts a proton (H+).

What is the general dissociation of an acid HA in water?

HA ⇌ H+ + A−.

What ion is hydrogen in water?

H+ (a proton).

What ion does a base produce in water?

OH− (hydroxide).

What characterizes a strong base versus a weak base?

Strong bases fully dissociate in water to yield OH−; weak bases only partially dissociate.

Give an example of a strong base.

Sodium hydroxide, NaOH.

What is a salt in acid-base chemistry?

A compound formed from the cation of a base and the anion of an acid (e.g., NaCl from NaOH and HCl).

How does HCl dissociate in water?

HCl → H+ + Cl−.

What is the autoionization of water at 25°C?

[H+] × [OH−] = 10^−14.

What is the pH of a neutral solution at 25°C?

pH = 7.

How is pH calculated?

pH = −log[H+].

What sign indicates an acidic solution on the pH scale?

pH < 7 (higher [H+], lower [OH−]).

What sign indicates a basic solution on the pH scale?

pH > 7 (higher [OH−], lower [H+]).

What is a buffer?

A solution that resists changes in pH, typically a weak acid and its conjugate base (or weak base and conjugate acid).

How does CO2 in water act as a buffer system?

CO2 forms carbonic acid (H2CO3), which equilibrates with bicarbonate (HCO3−) and H+, helping resist pH changes.

What are the basic components of a solution?

Solvent (the dissolving medium) and solute (the dissolved substance); solution = solvent + solute.

What is a salt and what ions form it?

A salt forms from the reaction of an acid and a base; it consists of the cation from the base and the anion from the acid.

What is an electrolyte?

A substance that forms ions in water and conducts electricity (salts, acids, or bases).

What is a nonelectrolyte?

A substance that dissolves in water but does not form ions.

What is a heterogeneous mixture?

A mixture that is not uniform throughout.

What is a homogeneous mixture?

A mixture that is uniform throughout.

What is hydrolysis?

A reaction in which water is added to break a bond between two molecules.

What is a condensation (dehydration synthesis) reaction?

A reaction in which two molecules are joined by the removal of water.