Principles of Chemistry Final Exam Review with Answers, Exams of Advanced Education

Download Principles of Chemistry Final Exam Review with Answers and more Exams Advanced Education in PDF only on Docsity! Principles of Chemistry Final Exam Review with Answers accuracy - correct answer-How close to the true value a given measurement is. precise - correct answer-How well a number of independent measurements agree with each other. atomic number - correct answer-(Z) • Number of protons in an atom's nucleus • Equivalent to the number of electrons around the atom's nucleus mass number - correct answer-(A) The sum of the number of protons (Z) and neutrons (N) in an atom's nucleus. A = Z + N isotope - correct answer-Atoms with identical atomic numbers but different mass numbers. (Different atoms of the same element can have different mass numbers depending on how many neutrons each has.) atomic weight - correct answer-The weighted average of the atomic masses of the element's naturally occurring isotopes. molar mass - correct answer-• Mass in grams of one mole of any element. • Numerically it is equivalent to its molecular or formula weight. • Use molar mass to convert between moles and grams. planck's postulate - correct answer-How to calculate the energy of a photon E = hν E = hc/λ • h (Planck's constant) = 6.626 × 10-34 J s • c = 3.00 x 108 m/s (speed of light) • λ (lambda) must be in meters! • 1 nm = 10-9 m principal quantum number - correct answer-(n) Distance from the nucleus! Describes the size and energy level of the orbital! • Positive integer (n = 1, 2, 3, 4, ...) • Commonly called shell • As the value of n increases: • The energy of the electron in the orbital increases • The distance of the electron from the nucleus increases angular momentum quantum number - correct answer-(l) Shape of the orbital! • Possible values (n = 0, 1, 2, 3, 4,..., (n-1) magnetic quantum number - correct answer-(m₁) Orientation in space! • Possible values (-l,...,-1, 0, 1,..., l) spin quantum number - correct answer-(m (subscript)s) Electron spin! • Possible values (-1/2, +1/2) electron configuration - correct answer-A description of which orbitals are occupied by electrons. ground-state electron configuration - correct answer-The lowest energy configuration. aufbau principle - correct answer-A set of guidelines for the filling order of orbitals. • Add electrons one-by-one to the lowest-energy orbital available. • An orbital can only hold two electrons, which must have opposite spins (Pauli exclusion principle). • If two or more orbitals of equal energy are available, one electron goes into each until all are half-full. The electrons in the half-filled orbitals are parallel. (Hund's rule) valence shell - correct answer-Outermost shell. • These electrons, as they are outermost and least tightly held, determine an element's properties. That is why elements in a given group have similar chemical properties. atomic radii - correct answer-Generally: • Increase going down a group because larger valence-shell orbitals are occupied. • Decrease going from left to right because the number of protons increases, which increases Zeff. effective nuclear charge - correct answer-Zeff = Zactual - Electron Shielding • Z represents nuclear charge • Zeff: nuclear charge actually felt by the electron • Zactual: full nuclear charge, pulls the electrons in double-headed arrow - correct answer-Indicates that the actual electronic structure is somewhere in between the two pictures drawn. formal charge - correct answer-The charge assigned to an atom in a molecule, assuming that electrons in all chemical bonds are shared equally between atoms, regardless of relative electronegativity. Note: This concept (Lewis dot structures) is not the same as oxidation number (redox). FC = (# of valence electrons in free atom) - (1/2)(# of bonding electrons) - (# of nonbonding electrons) VSEPR - correct answer-Valence-Shell Electron-Pair Repulsion model. Electrons in bonds and in lone pairs can be thought of as occupying "charge clouds," or regions of electron density, that repel one another and stay as far apart as possible, thus causing molecules to assume specific shapes. Working from an electron-dot structure, count the number of "charge clouds," and then determine the molecular shape. charge cloud - correct answer-Regions of electron density. • Count the number of the atom's bonds and lone pairs • Multiple bonds count the same as single bonds Remember: These things like to be as far apart from each other as possible. molecular shape - correct answer-The overall arrangement of atoms in the molecule. molecular geometry - correct answer-The arrangement of charge clouds on a specific atom. Note: Also referred to as electronic shape. valence bond theory - correct answer-A quantum mechanical model that shows how electron pairs are shared in a covalent bond. • The valence orbital of one atom, which has one electron, overlaps with the valence orbital of another atom, which also has one electron (of opposite spin). • The two electrons are attracted to the nuclei, which bonds the two atoms together. • The two electrons are shared. sigma bond - correct answer-(σ) A covalent bond formed by head-on overlap of orbitals. pi bond - correct answer-(π) A covalent bond formed by side-ways overlap of orbitals. hybridization - correct answer-The idea that atomic orbitals fuse to form newly hybridized orbitals, which in turn, influences molecular geometry and bonding properties. microscopic - correct answer-Considering how single atoms and molecules combine. macroscopic - correct answer-Equations can also refer to vast numbers of molecules. law of conservation of mass - correct answer-• In chemical reactions, mass is neither created nor destroyed. • Numbers and kinds of atoms on both sides of equation are the same. actual yield - correct answer-The amount of product actually formed in a reaction. theoretical yield - correct answer-The amount of product theoretically possible. percent yield - correct answer-=actual yield of product/theoretical yield of product × 100% • Must first calculate the theoretical yield to get this number. empirical formula - correct answer-Tells the smallest whole-number ratios of atoms in a compound (mole ratios). molecular formula - correct answer-Tells the actual numbers of atoms in a molecule. It can be either the empirical formula or a multiple of it. We can now add subscripts to our formula. • multiple = molecular weight / empirical formula weight molarity - correct answer-• The number of moles of a substance (solute) dissolved in one liter of solution • This term converts between moles of solute and liters of solution • = moles of solute / volume of solution (L) dilution - correct answer-The process of reducing the concentration of a solute in solution, usually simply by mixing with more solvent. concentrated solution + solvent dilute solution • The number of moles of solute remains constant upon dilution. • Initial moles of solute = final moles of solute • Mi x Vi = Mf x Vf (where M = mol/L, and V is in liters) titration - correct answer-A procedure for determining the concentration of a solution, by allowing a measured volume to react with a solution of another substance (the standard solution) whose concentration is known. strong electrolytes - correct answer-Compounds that dissociate to a large extent (70- 100%) into ions when dissolved in water. Strongly conducting. • Examples: HCl (strong acid), NaCl, KOH (strong base) weak electrolytes - correct answer-Compounds that dissociate to a small extent (1%) into ions when dissolved in water. Weakly conducting. • Example: CH3CO2H (acetic acid, weak acid) net ionic equation - correct answer-Equations that show only the soluble, strong electrolytes reacting (these are represented as ions) and omit the spectator ions, which go through the reaction unchanged. 1. Write the molecular equation: Write the formulas of the products, balance, assign physical states. 2. Write the ionic equation, dissociating the ionic compounds. 3. Eliminate the spectator ions from both sides of the equation. specific heat - correct answer-The amount of heat required to raise the temperature of 1 g of a substance by 1°C. • q = (mass of substance) x (specific heat) x ∆T • m = mass in grams • q = heat in Joules • ∆T = final temperature - initial temperature, in Celsius enthalpy change - correct answer-Also known as the heat of reaction or denoted by (∆H). • qp = ∆E + P∆V = ∆H • qp = transferred heat at constant pressure • ∆E = total change in the internal energy of a system • P∆V = pressures times change in volume thermodynamic standard state - correct answer-Most stable form of a substance at 1 atm pressure and at a specified temperature, usually 25°C; 1 M concentration for all substances in solution. standard enthalpy of reaction - correct answer-Indicated by the symbol ΔH°. Occurs when an enthalpy change measurement is made under thermodynamic standard state conditions. exothermic - correct answer-Heat (enthalpy) flows from the system to the surroundings. Final enthalpy less than initial. ΔH is negative. endothermic - correct answer-Heat (enthalpy) flows from the surroundings to the system. Final enthalpy greater than initial. ΔH is positive. Hess's Law - correct answer-The overall enthalpy change for a reaction is equal to the sum of the enthalpy changes for the individual steps in the reaction. This law can be used to calculate ΔH°.