Chemistry Regents Review Notes

Chemistry Regents Review Notes

General Information

• This review covers 12 core units.
• There are over 150 practice problems.
• It's recommended to have a reference table and to attempt problems before reviewing solutions.

Particle Diagrams

• Nitrogen Gas: Molecules should be drawn far apart and spread out with arrows indicating random movement.
• Liquid Nitrogen: Molecules should be drawn close together, possibly in a container.

Mixtures

• Separating Sand: Filtration can be used due to the varying particle sizes.
• Solubility & Reference Tables: Use Table G to determine solubility at specific temperatures.
• Mixture Types:
  • Homogeneous: Uniform distribution of molecules (e.g., saltwater).
  • Heterogeneous: Non-uniform distribution (e.g., sand in water).
• Varying Proportions: Mixtures can have different amounts of components (e.g., NH4Cl and sand).

Phase Changes and Heat Flow

• Sublimation: Direct change from solid to gas.
• Heat Flow: Heat flows from high to low temperatures.

Heat Transfer

• Equation: $\Delta Q = m \cdot c \cdot \Delta T$ (where $\Delta Q$ is change in energy, $m$ is mass, $c$ is specific heat capacity, and $\Delta T$ is change in temperature).
• Heat Transfer Direction: From surroundings to water if water temperature increases.

Kinetic Energy and Temperature

• Average kinetic energy is directly related to temperature.

Bright Line Spectra

• Production of Spectral Lines: Electrons move to higher energy levels (absorbing energy) and then fall back down (releasing energy as light).
• Spectra and Mass: Spectral lines are independent of mass; they depend on electron configuration.
• Identifying elements: If all lines match up with a mixture, we can say element is present in the mixture

Isotopes

• Isotopes of an element have the same number of protons but different numbers of neutrons.

Atomic Models

• Bohr and Thomson Models: Both describe electrons or small, negatively charged particles.
• Rutherford Model:
  • The nucleus is positive.
  • Atoms are mostly empty space.
  • Protons reside in the nucleus.
• First Model with Electrons: Thomson model.

Boron Isotopes

• Carbon-11 and Boron-11 differ in neutron number.
• Isotopic Notation: B mass Atomic Number.
• Isotopes with atomic mass closer to the average atomic mass are more abundant.

Chemical Bonding

• Metals lose electrons to become stable; nonmetals gain electrons.
• Lewis Dot Diagrams: Represent valence electrons in bonding.
• Nonpolar Molecules: Symmetrical distribution of charge.
• Ionic Compounds: Consist of a metal and a nonmetal.
• Elements in the same group have the same number of valence electrons.

Radii of Atoms and Ions

• Atomic radius increases down a group due to additional electron shells.
• Ions have fewer electron shells than their corresponding atoms, reducing radius.

Group 18 Elements

• Group 18 elements (noble gases) rarely form compounds because they have a full valence shell.

Molecular Polarity

• Polar molecules are soluble in polar solvents; nonpolar molecules are soluble in nonpolar solvents.
• Larger electronegativity differences result in more polar bonds.

Working with Density and Significant Figures

• When it comes to performing any mathematical multiplication or division, we have to round the amount of sig figs in each of the variables to the answer that has the least amount of sig figs as well
• Stronger intermolecular forces lead to higher boiling and melting points.

Mole Concepts and Calculations

• Mass percent: $\frac{mass \ of \ part}{mass \ of \ whole} * 100$.
• Finding Mass: If a balanced equation is given, we can find a mass of other things by converting grams to moles and using ratio and formula to convert moles to mass.
• Molarity equals the amount of moles of solute over the amount of liters of the solution
• Molarity = \frac{Moles \ of \ Solute}{Liters \ of \Solution}
• We can find an empirical formula which is a simplified molecular formula expression by looking for a common factor between two moles of the product as well
• We can also express percent error by doing Measured minus Accepted over Accepted times 100 and plugging it in to express that as well
• Gram formula mass for certain compounds can add an extra touch such that when you go down you want to add to the two full H2O