Key Concepts in Chemistry

SI Units

The International System of Units used globally for scientific measurement. Includes base units (e.g., meter, kilogram, second) and derived units (e.g., m/s, g/cm³).

metric prefixes

Prefixes that represent powers of ten, such as kilo- (10³), centi- (10⁻²), milli- (10⁻³), etc.

formula for density

Density (D) = Mass (m) / Volume (v)

Scientific vs Standard Notation

Scientific notation expresses numbers as a coefficient × 10^exponent. Standard notation is the usual decimal form.

convert units

Use dimensional analysis: multiply by conversion factors that cancel out unwanted units.

Accuracy vs Precision

Accuracy: how close a measurement is to the true value. Precision: how close repeated measurements are to each other.

Percent Yield vs Percent Error

Percent Yield = (Actual / Theoretical) × 100; Percent Error = Measured - True| / True × 100

Sig Fig Rules: Addition/Subtraction

Round to the least number of decimal places.

Sig Fig Rules: Multiplication/Division

Round to the least number of significant figures.

parts of a graph

Title, labeled axes, data points, and a line of best fit or smooth curve.

interpret a graph

Analyze trends, slopes, and relationships between variables.

Rules for naming binary acids

Prefix "hydro"; Root of the second element; Suffix "-ic"; Add "acid"

Rules for naming oxyacids

Identify polyatomic ion; Root name with prefix (if any); "-ate" → "-ic"; "-ite" → "-ous"; Add "acid"

Types of chemical equations

Word equation; Skeleton equation; Balanced chemical equation

coefficients in equations

The number of molecules or moles of each substance involved in the reaction.

Types of chemical reactions

Synthesis, Decomposition, Combustion, Single Replacement, Double Replacement

mole

The mole is a unit that measures the amount of substance

Mole

1 mole = 6.022 × 10²³ particles (atoms, molecules, etc.)

Conversion between moles and mass

Moles = Mass / Molar Mass

Conversion between moles and particles

Particles = Moles × 6.022 × 10²³

Percent composition

% Composition = (Mass of element / Mass of compound) × 100

Stoichiometry

The calculation of quantities in chemical reactions using balanced equations.

Molar ratio in reactions

The ratio of coefficients of substances in a balanced equation.

Limiting reactant

The reactant that produces the least amount of product; it runs out first.

Theoretical and percent yield

Theoretical yield: based on stoichiometry, Percent yield = (Actual / Theoretical) × 100

Kinetic Molecular Theory

Describes motion of gas particles: constant, random motion, negligible volume, elastic collisions.

Common pressure units and conversions

1 atm = 101.3 kPa = 760 mmHg = 760 torr

Boyle's Law

P₁V₁ = P₂V₂ (Pressure and Volume are inversely related)

Charles' Law

V₁/T₁ = V₂/T₂ (Volume and Temperature are directly related)

Gay-Lussac's Law

P₁/T₁ = P₂/T₂ (Pressure and Temperature are directly related)

Combined Gas Law

(P₁V₁)/T₁ = (P₂V₂)/T₂

Temperature conversion

K = °C + 273

Types of radiation

Alpha (α): ⁴₂He, Beta (β): ⁰₋₁e, Gamma (γ): energy, no mass or charge

Radioactive decay

Spontaneous breakdown of a nucleus into a more stable form, emitting radiation.

Half-life

Time it takes for half of a radioactive sample to decay.

Nuclear fission

Fission: nucleus splits (e.g., nuclear power)

Applications of nuclear reactions

Power generation, medical treatments, radiation therapy

Effects of radiation

Can cause mutations, cancer, or disease with high exposure

nuclear fusion

nuclei combine (e.g., stars)