Water & Solubility Lecture Review

A set of question-and-answer flashcards summarizing the key concepts on water’s structure, properties, solubility, heat capacity, and related chemical principles from the lecture notes.

What type of molecule is water in terms of polarity?

A small polar molecule with a permanent dipole.

Why does water have unusually high boiling and melting points for its size?

Extensive hydrogen bonding between water molecules requires extra energy to break.

What is meant by water being the “universal solvent”?

It dissolves many ionic and polar covalent substances because they can interact with water via ion-dipole attractions or hydrogen bonding.

Name two interactions that allow solutes to dissolve in water.

Hydrogen bonding (e.g., NH₃ with H₂O) and ion-dipole attraction (e.g., Na⁺, Cl⁻ with H₂O).

Define latent heat of fusion for water and give its value.

Energy needed to change 1 mol of ice to liquid at 0 °C; about 6 kJ mol⁻¹.

Define latent heat of vaporization for water and give its value.

Energy needed to convert 1 mol of liquid water to vapour at 100 °C; about 44 kJ mol⁻¹.

How do high latent heat values of water help regulate Earth’s climate?

Phase changes absorb or release large amounts of heat, buffering temperature swings.

What is specific heat capacity?

Energy required to raise the temperature of 1 g of a substance by 1 °C.

What is the specific heat capacity of water?

4.18 J g⁻¹ °C⁻¹.

Write the heat energy equation that uses specific heat capacity.

q = m c ΔT (heat = mass × specific heat capacity × temperature change).

Why does the large heat capacity of oceans moderate coastal climates?

Water absorbs heat by day and releases it at night, limiting daily temperature variation.

Give the balanced equation for photosynthesis.

6 CO₂ + 6 H₂O → C₆H₁₂O₆ + 6 O₂.

Give the balanced equation for aerobic respiration.

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O.

List three biological functions of water in organisms.

Transports nutrients/wastes, transfers & stores heat, cools the body via evaporation (sweating).

Which chloride salts are insoluble in water according to the solubility table?

AgCl, Hg₂Cl₂, and PbCl₂.

Name four sulfate salts that are insoluble or only slightly soluble.

CaSO₄, BaSO₄, HgSO₄, PbSO₄ (Ag₂SO₄ is slightly soluble).

What is the general solubility trend for Group 1 metal and ammonium salts?

They are all soluble in water.

Why does AgCl precipitate when NaCl(aq) and AgNO₃(aq) are mixed?

Ag⁺ and Cl⁻ form insoluble AgCl, while Na⁺ and NO₃⁻ remain as spectator ions.

How does temperature usually affect the solubility of solid solutes?

For most solids, solubility increases as temperature rises (curve slopes upward).

How does temperature affect the solubility of gases in water?

Gas solubility decreases with increasing temperature (curves slope downward).

On a solubility curve, what does a point above the line indicate?

A supersaturated solution containing more solute than equilibrium allows.

What does ‘slightly soluble’ mean in a solubility table?

Less than about 0.1 mol of solute dissolves per 100 g of water; a precipitate readily forms.

State two key trends from the solubility table.

(1) Group 1 and NH₄⁺ salts are soluble. (2) Many Ag⁺, Pb²⁺, and Hg₂²⁺ salts are insoluble.

Which property of water allows it to store large amounts of heat with little temperature change?

Its high specific heat capacity due to extensive hydrogen bonding.

Why does sweating cool the human body?

Evaporation of water uses the latent heat of vaporization, drawing heat away from the skin.

What type of bonding occurs between neighboring water molecules?

Hydrogen bonding between the δ⁺ hydrogen of one molecule and the δ⁻ oxygen of another.

Why do metals generally have lower specific heat capacities than water?

They lack strong intermolecular hydrogen bonds, so less energy is needed to raise their temperature.

Why are coastal temperatures milder than inland temperatures?

Large bodies of water moderate climate through high heat capacity and latent heat effects.