General Chemistry Fundamentals: Concepts, Calculations, and Applications

Chemical Tools: Experimentation & Measurement

Significant Figures and Measurement

Accurate measurement and reporting of data are foundational in chemistry. Significant figures reflect the precision of a measured value.

• Significant Figures: The digits in a measurement that are known with certainty plus one digit that is estimated.

• Example: Reading a ruler to measure the length of a metal bar, the correct number of significant figures depends on the smallest marked division and estimation.

• Accuracy vs. Precision: Accuracy refers to how close a measurement is to the true value, while precision refers to how reproducible measurements are.

Density Calculations

Density is a physical property defined as mass per unit volume.

• Formula: $\text{Density} = \frac{\text{Mass}}{\text{Volume}}$

• Application: Used to identify substances and convert between mass and volume.

• Example: If a piece of silver has a mass of 52.0 g and a density of 10.5 g/cm3, its volume is $\frac{52.0\ \text{g}}{10.5\ \text{g/cm}^3} = 4.95\ \text{cm}^3$.

Atoms, Molecules & Ions

Atomic Structure and Isotopes

Atoms consist of protons, neutrons, and electrons. Isotopes are atoms of the same element with different numbers of neutrons.

• Atomic Number (Z): Number of protons in the nucleus.

• Mass Number (A): Sum of protons and neutrons.

• Isotope Notation: $^{A}_{Z}\text{X}$, where X is the element symbol.

• Example: $^{39}_{19}\text{K}$ has 19 protons, 20 neutrons, and 19 electrons.

Average Atomic Mass

The average atomic mass of an element is calculated using the masses and abundances of its isotopes.

• Formula: $\text{Average Atomic Mass} = \sum (\text{isotope mass} \times \text{fractional abundance})$

• Example Table:

Isotope	Abundance (%)	Mass (amu)
Al-26	15.0	25.98
Al-27	75.0	26.98
Al-28	10.0	27.98

• Calculation: $0.15 \times 25.98 + 0.75 \times 26.98 + 0.10 \times 27.98$

Mass Relationships in Chemical Reactions

Stoichiometry

Stoichiometry involves quantitative relationships between reactants and products in chemical reactions.

• Mole Concept: 1 mole = $6.022 \times 10^{23}$ particles.

• Balanced Equations: Used to determine the ratios of reactants and products.

• Example: $2\text{Al} + 3\text{Cl}_2 \rightarrow 2\text{AlCl}_3$

• Limiting Reactant: The reactant that is completely consumed first, limiting the amount of product formed.

• Calculation: Given masses of reactants, convert to moles, use stoichiometry to find limiting reactant and amount of product.

Law of Definite Composition

This law states that a chemical compound always contains the same proportion of elements by mass.

• Application: Used to confirm the identity of compounds and their formulas.

Reactions in Aqueous Solution

Types of Chemical Reactions

Chemical reactions can be classified as precipitation, acid-base, or redox reactions.

• Precipitation Reaction: Formation of an insoluble product (precipitate) from soluble reactants.

• Example: $\text{PbCO}_3 (s)$ forms from $\text{Pb(NO}_3)_2$ and $\text{Na}_2\text{CO}_3$ in solution.

Atoms, Molecules & Ions: Nomenclature

Naming Compounds

Chemical nomenclature follows specific rules for ionic and molecular compounds.

• Ionic Compounds: Name the cation first, then the anion. Use Roman numerals for transition metals.

• Molecular Compounds: Use prefixes to indicate the number of atoms.

• Acids: Naming depends on the anion: -ide becomes hydro-...-ic acid, -ate becomes ...-ic acid, -ite becomes ...-ous acid.

• Example Table:

Formula	Name
Pb(NO3)2	Lead(II) nitrate
K2SO4	Potassium sulfate
NaCl	Sodium chloride

Periodicity & Electronic Structure of Atoms

Periodic Table Organization

The periodic table arranges elements by increasing atomic number and groups elements with similar properties.

• Groups: Vertical columns; elements in the same group have similar chemical properties.

• Periods: Horizontal rows.

• Metals, Nonmetals, Metalloids: Metals are on the left, nonmetals on the right, metalloids border the staircase.

• Example: The shaded area in a periodic table may indicate metals.

Lab Techniques and Procedures

Physical vs. Chemical Changes

Physical changes do not alter the chemical identity, while chemical changes result in new substances.

• Physical Change: Changes in state or appearance (e.g., melting, boiling).

• Chemical Change: Formation of new substances (e.g., rusting, combustion).

• Example: Decomposition of sodium hydrogen carbonate is a chemical change.

Mathematical Operations and Functions

Scientific Notation

Scientific notation expresses numbers as a product of a coefficient and a power of ten.

• Example: $1.800 \times 10^3$

Covalent and Ionic Bonding

Types of Chemical Bonds

Chemical bonds include ionic, covalent, and metallic bonds, each with distinct properties.

• Ionic Bond: Transfer of electrons from metal to nonmetal.

• Covalent Bond: Sharing of electrons between nonmetals.

• Metallic Bond: Delocalized electrons among metal atoms.

• Example: K2SO4 contains ionic bonding.

Additional info:

• Some questions reference specific chemical reactions and calculations, which are foundational for stoichiometry and chemical nomenclature.

• Periodic table questions reinforce understanding of element classification and periodic trends.

• Questions on isotopes and atomic mass support mastery of atomic structure concepts.