Chemistry Exam Review: Significant Figures, Isotopes, and Moles

A comprehensive set of flashcards covering significant figures, isotopes, atomic mass, and mole concepts as outlined in the lecture notes.

Significant Figures

Digits in a number that contribute to its precision.

Exact Numbers

Numbers obtained through counting; have infinite significant figures.

Approximate Numbers

Numbers obtained through measurement; their precision must be evaluated.

Captive Zeros

Zeros that are always significant when they occur between non-zero digits.

Leading Zeros

Zeros that precede all non-zero digits and are NEVER significant.

Trailing Zeros in Decimals

Zeros following a decimal point in a number are significant.

Trailing Zeros in Whole Numbers

Zeros at the end of a whole number are NOT significant unless a decimal point is present.

Precision

The reproducibility of a measurement; how closely repeated measurements agree.

Accuracy

How close a measurement is to the actual value.

Uncertainty

An estimate of how much a measure could vary from the actual value.

Scientific Notation

A way to express numbers as a product of a number between 1 and 10 and a power of ten.

SI Units

International System of Units, a standardized metric system.

Molar Mass

The mass of one mole of a substance expressed in grams per mole (g/mol).

Isotope

Atoms of the same element that have different numbers of neutrons.

Mass Number

The total number of protons and neutrons in an atom.

Atomic Mass Unit (u)

A unit of mass used to express atomic mass, defined as one twelfth of the mass of a carbon-12 atom.

Isotopic Abundance

The relative amount of a specific isotope of an element in a sample.

Average Atomic Mass

The weighted average of the masses of an element's isotopes.

Conversion Factor

A ratio used to convert from one unit to another.

Avogadro's Number

The number of particles in one mole: $6.022 imes 10^{23}$.

Mole

A unit used to describe the amount of substance containing $6.022 imes 10^{23}$ representative particles.

Representative Particle for an Element

An atom.

Representative Particle for a Molecular Compound

A molecule.

Representative Particle for an Ionic Compound

A formula unit.

Volume of Gas

The amount of space occupied by gas particles, affected by temperature and pressure.

Standard Temperature and Pressure (STP)

0°C (273K) and 1 atm pressure.

Molar Volume

The volume occupied by one mole of a gas at STP, which is $22.4 ext{ L}$.

Accuracy vs Precision

Accuracy refers to closeness to a true value; precision refers to consistency across repeated measurements.

Estimated Digit

The last digit in a reported measurement, which is uncertain.

Least Count

The smallest division of measurement on an instrument.

Instrument Limit of Error (ILE)

Represents the uncertainty in the measurement, usually calculated from Least Count.

Molar Mass of Compound

The sum of the molar masses of all elements in the compound.

Calculating Average Atomic Mass

Multiply the mass of each isotope by its relative abundance, convert abundance to decimal, and add the totals.

Uncertainty in Measurement

Expressed as a range reflecting possible variation from the true value.

Unit Analysis

A method that uses conversion factors to convert measurements from one unit to another.

Conversion Factors for Length

1 km = 1000 m, 1 m = 100 cm.

Conversion Factors for Volume

1 L = 1000 mL, 1 mL = 1 cm³.

Conversion Factors for Mass

1 kg = 1000 g.

Conversion Factors for Time

1 h = 60 min, 1 min = 60 s.

Quantitative Measurements

Measure of the quantity of something, often given in numbers with units.

Qualitative Measurements

Describes the qualities of something, often using words.

Combining Molar Mass and Moles

Use molar mass to convert between the mass of a substance and moles.

Molar Mass of Sodium Chloride (NaCl)

The mass of one mole of NaCl is numerically equal to its molar mass in g.

Mass of Carbon in Molecules

Mass can be determined from the number of molecules using molar mass.

Calculation of Moles from Mass

Divide the mass by the molar mass to get the number of moles.

Molar Mass Calculation

Sum the molar masses of each element present in a compound.

Henry's Law

At constant temperature, the amount of gas that dissolves in a liquid is proportional to the partial pressure of that gas above the liquid.

Empirical Formula

The simplest whole-number ratio of atoms of each element in a compound.

Molecular Formula

The actual ratio of atoms of each element present in a compound.

Dilution

Reducing the concentration of a solute in a solution, usually by adding more solvent.

Stoichiometry

The calculation of reactants and products in chemical reactions.

Limiting Reactant

The reactant that is completely consumed in a reaction, limiting the amount of product formed.

Exothermic Reaction

A reaction that releases energy in the form of heat.

Endothermic Reaction

A reaction that absorbs energy from its surroundings.

Electrolytes

Substances that dissociate into ions in solution, conducting electricity.

Phase Diagram

Graphs that show the state of a substance at different temperatures and pressures.

Combustion Reaction

A chemical reaction that involves the burning of a substance in the presence of oxygen.

Hydration Energy

The energy released when ions are surrounded by water molecules.

Ionization Energy

The energy required to remove an electron from an atom or ion.

Chemical Equilibrium

The state in which the concentrations of reactants and products remain constant over time.

Dynamic Equilibrium

The state of balance between continuing processes, such as forward and reverse reactions occurring at equal rates.

Catalyst

A substance that increases the rate of a chemical reaction without being consumed.

Le Chatelier's Principle

If a dynamic equilibrium is disturbed by changing the conditions, the position of equilibrium shifts to counteract the change.

Atom Economy

A measure of the efficiency of a reaction in converting reactants into useful products.

Green Chemistry

The design of chemical products and processes that reduce or eliminate the use and generation of hazardous substances.

Scalability in Chemistry

The capacity to scale up reactions to industrial levels without losing efficiency or safety.

Safety Data Sheets (SDS)

Documents that provide information on the properties of hazardous chemicals.

Waste Disposal Methods in Chemistry

Techniques used to effectively and safely dispose of chemical waste.

Bioaccumulation

The accumulation of substances, such as pesticides or other chemicals, in an organism.

Titration

A technique where a solution of known concentration is used to determine the concentration of an unknown solution.

Spectroscopy

A technique used to measure the interaction of light with matter to identify and quantify substances.

Chromatography

A method for separating components of a mixture based on their different interactions with a stationary phase.

Reagent

A substance used to cause a chemical reaction.

Synthesis Reaction

A reaction in which two or more simple substances combine to form a more complex product.

Decomposition Reaction

A reaction in which a single compound breaks down into two or more simpler products.

Hydrolysis Reaction

A reaction with water that results in the breakdown of a compound.

Redox Reaction

A reaction involving the transfer of electrons between two species.