Experimental Chemistry, Atomic Structure, Bonding, Mole Concept, Acids and Salts

Upward Delivery

A gas collection method used for gases that are less dense than air.

Downward Delivery

A gas collection method used for gases that are more dense than air.

Delivery Through Water

A gas collection method used for gases that are insoluble in water.

Calcium Chloride ($\text{CaCl}_2$) Drying Agent

A drying agent that cannot be used to dry ammonia ($\text{NH}_3$).

Sulfuric Acid ($\text{H}_2\text{SO}_4$) Drying Agent

A drying agent that cannot be used to dry basic gases or ammonia ($\text{NH}_3$).

Calcium Oxide ($\text{CaO}$) Drying Agent

A drying agent that cannot be used to dry sulfur dioxide ($\text{SO}_2$) or acidic gases.

Sublimation (Separation Technique)

A solid-to-gas separation method applicable ONLY to iodine, mothballs, dry ice, and naphthalene.

Magnetic Attraction

A solid-solid separation method applicable ONLY to iron, cobalt, nickel, and steel.

Separating Funnel

A liquid-liquid separation apparatus used to separate immiscible liquids that cannot dissolve in each other.

Retention Factor ($R_f\text{ Value}$)

In chromatography, calculated as $\frac{\text{distance travelled from the start point}}{\text{solvent front}}$.

Arrangement of Particles in Solid, Liquid, and Gas States

Solids have tightly packed, orderly arranged particles; liquids have closely packed, randomly arranged particles; gases have widely spaced, randomly arranged particles.

Endothermic Phase Changes

State changes that take in energy, including melting (solid $\rightarrow$ liquid), boiling (liquid $\rightarrow$ gas), and sublimation (solid $\rightarrow$ gas).

Exothermic Phase Changes

State changes that lose energy, including deposition (gas $\rightarrow$ solid), freezing (liquid $\rightarrow$ solid), and condensation (gas $\rightarrow$ liquid).

Factors Affecting Diffusion

The three physical factors influencing diffusion rate: mass, temperature, and concentration gradient.

Subatomic Particles

Protons (charge $+1$, relative mass $1$, in nucleus), neutrons (charge $0$, relative mass $1$, in nucleus), and electrons (charge $-1$, relative mass $\frac{1}{1840}$, in electron shells).

Isotopes

Atoms of the same element with the same number of protons but a different number of neutrons, possessing identical chemical properties but different physical properties.

Cation and Anion

A cation is a positively charged ion formed by metals; an anion is a negatively charged ion formed by non-metals.

Ionic Bonding

Bonding in compounds characterized by high melting/boiling points due to strong electrostatic attraction, solubility in water (insoluble in organic solvents), electrical conductivity in liquid/aqueous states due to mobile ions, and a hard, brittle structure.

Covalent Bonding

Bonding in elements or compounds characterized by low melting/boiling points due to weak intermolecular forces, solubility in organic solvents (insoluble in water), and non-conductivity of electricity.

Metallic Bonding

Bonding in metals characterized by high melting/boiling points, strong electrostatic attraction, insolubility in water, electrical conductivity via a sea of delocalised electrons, and malleability/ductility because atoms are orderly arranged and can slide past each other.

Graphite

An elemental structure with a high melting/boiling point, insolubility in water, electrical conductivity due to free electrons, and a soft, slippery texture due to weak intermolecular forces between layers.

Diamond

An elemental structure with a high melting/boiling point, insolubility, electrical non-conductivity, and hard, brittle structure due to strong covalent bonds.

Relative Atomic Mass ($A_r$)

The mass of an atom defined relative to $\frac{1}{12}$ of a carbon atom, or calculated as the sum of ($\% \times \text{isotopic mass}$).

Molar Gas Volume at R.T.P.

The volume occupied by $1\,\text{mole}$ of any gas at room temperature and pressure, equal to $24\,\text{dm}^3$ or $24000\,\text{cm}^3$.

Avogadro's Constant

The number of particles contained in $1\,\text{mole}$, equal to $6.02 \times 10^{23}$.

Percentage Purity

Calculated using the formula $\frac{\text{actual mass}}{\text{total mass}} \times 100\%$.

Percentage Yield

Calculated using the formula $\frac{\text{actual yield}}{\text{theoretical yield}} \times 100\%$.

Limiting Reagent

The reactant in a chemical reaction that is completely consumed first and determines the amount of product formed.

Acid

A substance that dissociates $\text{H}^+$ ions in water, has $\text{pH} < 7$, turns blue litmus red, and is corrosive when concentrated; strong acids ($\text{HCl}$, $\text{H}_2\text{SO}_4$) fully ionise while weak acids ($\text{HNO}_3$, $\text{H}_2\text{CO}_3$, $\text{C}_2\text{H}_5\text{COOH}$) partially ionise.

Alkali

A substance that dissociates $\text{OH}^-$ ions in water, has $\text{pH} > 7$, turns red litmus blue, feels soapy, tastes bitter, and is corrosive when concentrated; strong alkalis include $\text{NaOH}$, $\text{Ca(OH)}_2$, $$\text{NH}_4\text