Chemistry Final Exam Key Terms

Chemistry Final Exam Key Terms Study Guide flashcards

Solute

A substance that is dissolved in a solvent.

Solvent

The substance that dissolves the solute; usually present in greater amount.

Solution

A homogeneous mixture of solute and solvent.

Molarity (M)

Moles of solute per liter of solution.

Molality (m)

Moles of solute per kilogram of solvent.

Dilution

The process of decreasing the concentration of a solution (M₁V₁=M₂V₂).

Saturated solution

A solution that contains the maximum amount of solute.

Unsaturated solution

A solution that can dissolve more solute.

Supersaturated solution

A solution that holds more solute than it normally should at that temperature.

Like dissolves like

Polar solvents dissolve polar solutes; nonpolar dissolves nonpolar.

Colligative properties

Properties that depend on the number of solute particles (e.g., boiling point elevation, freezing point depression).

q (heat)

Energy transferred due to temperature difference.

Specific heat (c)

The energy needed to raise 1g of a substance by 1°C.

Exothermic

Releases heat; ΔH is negative.

Endothermic

Absorbs heat; ΔH is positive.

Enthalpy (ΔH)

Heat content of a system.

Entropy (ΔS)

Measure of disorder or randomness.

Gibbs Free Energy (ΔG)

Determines spontaneity: ΔG = ΔH - TΔS

Spontaneous reaction

Occurs without outside energy input; ΔG < 0.

System

The part of the universe being studied.

Surroundings

Everything else outside the system.

Acid

Donates H+ ions (protons).

Base

Accepts H+ ions.

Brønsted-Lowry acid

Proton donor.

Brønsted-Lowry base

Proton acceptor.

Conjugate acid

Formed when a base gains a proton.

Conjugate base

What remains after an acid donates a proton.

Neutralization

Reaction of acid and base to form water and salt.

pH

Measure of hydrogen ion concentration; scale from 0-14.

pOH

Measure of hydroxide ion concentration.

Kw

Ionization constant of water: 1.0 × 10⁻¹⁴ at 25°C.

Strong acid/base

Fully dissociates in solution.

Weak acid/base

Partially dissociates in solution.

Titration

Technique to find unknown concentration using a neutralization reaction.

Equivalence point

Point at which moles of acid = moles of base.

Reactants

Substances that undergo a change.

Products

Substances formed after the reaction.

Synthesis reaction

Two or more substances combine to form one.

Decomposition reaction

A compound breaks into two or more parts.

Single Replacement

One element replaces another in a compound.

Double Replacement

Two ionic compounds switch partners.

Combustion

Hydrocarbon + O₂ → CO₂ + H₂O

Precipitate

Solid that forms from a solution.

Spectator ion

Ion that does not participate in the reaction.

Balanced equation

Has equal atoms of each element on both sides.

Law of Conservation of Mass

Mass is neither created nor destroyed.

Mole

6.022 x 10²³ particles (Avogadro's number).

Avogadro's number

Number of units in one mole.

Molar mass

Mass of one mole of a substance (g/mol).

Percent composition

Percent by mass of each element in a compound.

Empirical formula

Simplest whole number ratio of atoms in a compound.

Molecular formula

Actual number of atoms of each element in a compound.

Conversion factor

Used to convert between grams, moles, atoms, etc.

Dimensional analysis

A method to solve problems using conversion factors.

Boyle's Law

P₁V₁ = P₂V₂ (Pressure inversely related to volume).

Charles's Law

V₁/T₁ = V₂/T₂ (Volume directly related to temp).

Gay-Lussac's Law

P₁/T₁ = P₂/T₂ (Pressure directly related to temp).

Combined Gas Law

(P₁V₁)/T₁ = (P₂V₂)/T₂

Ideal Gas Law

PV = nRT

STP

Standard Temperature and Pressure: 0°C (273 K), 1 atm.

R (gas constant)

0.0821 L·atm/mol·K

Partial pressure

Pressure contributed by one gas in a mixture.

Dalton's Law

Total pressure = sum of individual gas pressures.

Kinetic Molecular Theory

Gas particles move constantly and randomly, with negligible volume.

Stoichiometry

The calculation of reactants and products in a chemical reaction.

Mole ratio

Ratio of moles of substances from a balanced equation.

Limiting reactant

Reactant that runs out first and limits the amount of product.

Excess reactant

Reactant left over after the reaction stops.

Theoretical yield

Maximum amount of product that could form.

Actual yield

The amount of product actually obtained.

Percent yield

(Actual Yield / Theoretical Yield) x 100

Balanced equation

Required for stoichiometry problems to use mole ratios correctly.