Download Atomic Structure and Chemical Bonding and more Exams Chemistry in PDF only on Docsity!
TExES Chemistry 7-12 (240) Practice
Test study a-head solution
alpha decay - --nucleus emits an alpha particle with 2 protons and 2 neutrons, leaving the rest of the nucleus behind. atomic number of the isotope decreases by 2 and the mass by 4. energy carried away in the form of kinetic beta decay - --a neutron changes into a proton by emitting an electron and a neutrino from the nucleus. the atomic # of the isotope increases by 1 but the mass stays the same. gamma decay - --electromagnetic energy is released from the nucleus in the form of a gamma ray. atomic # and mass do not change half life - --initial amount (.5)^(time elapsed/half life) Carbon dating - --half-lives to determine the approximate age of fossils under 70,000 years. Carbon-14 which is an unstable isotope of carbon has a half-life of about 5,000 years. density - --the amount of mass present in a given volume. Reflection of how tightly packed the atoms are. water density - --Water has a density of 1 gram per cubic centimeter. hardness - --the mineral's resistance to scratching; measured on the Mohs scale, where talc, the softest mineral, has a score of 1 and diamond, the hardest, has a score of 10 diamond is hard, talc is soft
radioactivity - --When an atom changes the number of protons in the nucleus and releases radiation; used in medicine alpha particles - --the least dangerous to humans when exposed externally because of its low penetrating power xray - --high-energy rays that can penetrate the skin and organs and can be used for medical imaging. radiometric dating - --The age of very old igneous rocks can be determined; half-lives of the parent isotopes in the rock, ratio of the amounts of parent and daughter isotopes in the rock John Dalton - --spherical atom JJ Thompson - --plum pudding theory; atom is spherical, but proton, neutrons and electrons were floating like fruits Rutherford - --identified nucleus; positive particles concentrated in the center of an atom Bohr - --fixed rutherford; added electron rings (planetary model) Schrodinger - --Quantum Model; electrons move in waves around the nucleus rather than fixed orbitals transition metals - --solid at room temp, conductors shiny malleable
Formal charge - --charge of each atom in the molecule, assuming that electrons are shared equally in covalent bonds; Valence Electrons - [Non-bonding electrons + (# of Bonds)] photoelectric effect - --Electrons are ejected from a metal when light shines on them at a high enough frequency wave model of light - --The description of light as a wave with a frequency and wavelength particle model of light - --The description of light as a particle with a definite location; Each particle's energy was proportional to the constant h (6.63 x 10^-34 m^2kg/s) and the frequency, f, of the light; a photon's energy cannot be shared among electrons, nor can an electron "store up" energy from multiple photons. entanglement - --Entangled particles instantly share information with each other even when separated by a great distance atomic radius - --the distance from the nucleus to the outer electron shell ground state - --the lowest-energy arrangement of electrons in an atom threshold frequency - --The minimum frequency for which electrons are ejected from a metal during the photoelectric effect group 1, alkali metals - --react to form a basic solution when mixed with water plasma - --electrons are stripped from their orbits around the nuclei of atoms and are allowed to move freely throughout the material.
Kinetic Molecular Theory of Matter - --Kinetic energy and speed increase as temperature increases. PâTâ1/V ideal gas law - --PV=nRT ; where P is pressure, V is volume, n is the number of moles of gas, R is the gas constant, and T is temperature in Kelvin. Boyle's law - --relationship between pressure and volume. P1V1 = P2V2 at constant temperature. Charles' law - --the relationship between volume and temperature. V1/T1 = V2/T2 at constant pressure. As pressure increases - --the volume decreases. If volume increases - --the temperature increases. daltons law -- partial pressure - --Ptotal = P1 + P2 + P3... standard temperature and pressure (STP) - --273 oK ( 0 oC, 32 oF) and 1 atm. At STP conditions one mole of gas, regardless of chemical identity, will have a volume of 22.4 L. reaction profile - --Î concentration / Î time
Catalysts - --speed up chemical reactions by reducing Ea, and they are not consumed in the reaction. Enzymes - --biological catalysts that facilitate biochemical reactions in cells. Enzymes have active sites with specific conformations, which position the reacting molecules favorably to induce a chemical reaction. Most enzyme catalysts are composed of protein, but some RNA molecules also have catalytic functions. Standard enthalpy of formation (ÎHfo) - --the quantity of heat associated with the formation of 1 mole of a chemical from its component elements. Standard enthalpy of reaction (ÎHrxno) - --the difference in standard enthalpies of formation in a chemical reaction Exothermic - --enthapy of products < enthapy of reactants; negative enthapy of reaction; heat released Endothermic - --enthapy of products > enthapy of reactants; positive enthapy of reaction ; heat absorbed enthalpy of solution or enthalpy of dissolution (ÎHsoln). - --The process of dissolving a solute in a solvent can be exothermic or endothermic. The heat that is absorbed or released during dissolution Breaking bonds between and within solute molecules - --endothermic because it requires energy.
Attractive forces between solute and solvent molecules; intermolecular bonds - --exothermic because it releases energy. KOH - ---57.6, exothermic LiBr - ---48.8, exothermic LiCl - ---37, exothermic NaBr - ---0.6, exothermic NaCl - --3.9, endothermic KCl - --17.2, endothermic KBr - --19.9, endothermic exothermic dissolution - --interactions between the solute particles are weaker than the interactions between solute and solvent particles. The ÎHsoln is negative. endothermic dissolution - --the interactions between solute particles are stronger than the interactions between solute and solvent particles. The ÎHsoln is positive. specific heat (c) - --The change in thermal energy when a substance heats or cools is proportional to the mass and the temperature change of the substance. ÎQ = mcÎT
zeroth law of thermodynamics - --if two bodies are in thermal equilibrium with a third body, then they are in thermal equilibrium with each other. Bodies in thermal equilibrium do not exchange heat, even when touching each other. The zeroth law allows scientists to use a thermometer (the third body) to measure and compare the temperatures of two other bodies that are not in thermal contact with each other. first law of thermodynamics - --the change in the internal energy ÎU of a closed system equals the heat Q added to the system minus the work W done by the system. ÎU = Q - W when work is done BY a system - --the systems internal energy decreases when work is done ON a system - --the system increases internal energy second law of thermodynamics - --which processes can happen spontaneously in nature and which cannot; why your hot pizza doesn't get warmer as it sits on the table waiting for you to eat;; cannot be 100% efficient during the process of bringing two objects into thermal equilibrium - --entropy increases entropy - --as the tendency of a system to move from order to disorder; the amount of thermal energy that cannot be used to do mechanical work as a system moves toward equilibrium. Crystals - --when metals and nonmetals bond to create a repeating 3D pattern. The strength of the atomic bonds holding the together determines solubility and density.
Polymers - --long repeating chains of molecules; man-made items such as plastic bottles and cups. Polymers are also found in nature. For example, DNA and spider webs are both polymers. Covalent bonds - --when electrons are shared between 2 atoms and the bond is classified as polar or nonpolar. Pauling Units (PU) - --used to measure the electronegativity of a bond. polar covalent bond - --involves 2 different types of atoms and occurs when one atom has a stronger pull on the electron, or a greater electronegativity. The stronger atom will have a slightly negative charge and the other atom(s) will be slightly positive which results in poles on the molecule. Polar bonds have a measurement of 0.5-1.9 PU. nonpolar covalent bond - --between 2 atoms of the same element, which pull equally on the electron. Non-polar bonds have a measurement of <0.5PU. Ionic bonds - --one atom gives up one or more electrons and another atom accepts the electron. These oppositely charged ions attract each other resulting in a bond. cation - --positively charged atom anion - --negatively charged atom Metallic bonds - --between 2 metal atoms of the same or different elements. The metals give up electrons which causes them to have a positive charge. These floating electrons are what allows metals to conduct electricity well and be malleable.
Intramolecular - --act within molecules between individual atoms. They are stronger than intermolecular forces. Steric number - --calculated by adding the number of attached atoms to the number of lone pair VSEPR (valence shell electron pair repulsion) theory - --lone pairs take up more space than atomic substituents, which affects molecular geometry. When bond dipoles are symmetrical - --a molecule does not have a molecular dipole. ionic bond names - --metal is named first and then the non-metal with the ending -ide. nonmetal bond names - --positively charged particle is named first and the elements are given prefixes to show how many atoms are present. The second element is given the suffix - ide. The first element does not get a prefix if it only has 1 atom. base names - --usually have hydroxide (OH) in them so they are named in the same way an ionic bond is named. The first element name is stated followed by hydroxide. acid names - --for the hydrogen atom(s) and the ion. Hydrogen is represented by the prefix hydro-. The first syllable of the ion is attached. Finally, -ic is added as a suffix to the word. Polyatomic ions - --Molecules with a non-zero charge that form from more than one atom monomers - --single units
polymers - --linkd of monomers lipids - --stored energy, fatty acid monomers, phospholipid polymer Carbohydrates - --quick energy, monosaccharide, polysaccharide Proteins - --carry out cellular functions, amino acid monomer, polypeptide chain polymer (enzymes) nucleic acids - --store and carry genetic material, nucleotide (a, t, c, g, u), DNA/RNA Molecular Dipole - --Describes the distribution of charge on a molecule and is determined by molecular geometry and the individual bond dipoles molecular forces from weakest to strongest - --London dispersion forces are the weakest molecular force. Hydrogen bonding is stronger than LDF, but still weaker than intramolecular metallic bonding. electron density - --decreases as a function of distance from the nucleus p subshell - --three equivalent orbitals that are perpendicular s subshell - --only one orbital bond energy of products < reactants - --exothermic
hydroiodic acid - --hi nitric acid - --HNO sulfuric acid - --H2SO chlorous acid - --HClO nitrous acid - --HNO insoluable compounds - --sulfides, carbonates (except group 1), phosphates, hydroxides Combination - --2 elements or molecules combine to form 1 molecule A + B â AB Decomposition - --1 molecule is broken down into 2 separate elements or molecules AB->A+B Single Replacement - --One element or molecule replaces another element in a molecule A + BC --> B + AC Double Replacement - --Elements in molecules replace each other AB + CD = AD + CB
Combustion - --A compound containing carbon reacts with oxygen and burns, releasing carbon dioxide Oxidation/Reduction (Redox) - --A transfer of electrons that changes the oxidation number (charge) of the atom from the reactant to the product side. Neutralization - --An acid and a base react to form water and salt with a pH level of 7 reduction - --gain of electrons oxidation - --loss of electrons Rate laws - --Rate = k[A]m[B]n Gibbs free energy (ÎG) - --equal to the change in enthalpy minus the product of temperature and the change in entropy ÎG = ÎH - TÎS ÎG < 0 - --ÎGproducts < ÎGreactants and the reaction is spontaneous. ÎG = 0 - --ÎGproducts = ÎGreactants and the reaction is at equilibrium. ÎG > 0 - --ÎGproducts > ÎGreactants and the reaction is not spontaneous.
Decreasing the temperature of an endothermic reaction - --favor reactant formation because product formation requires an input of heat from the reactant side. When the pressure is increased - --equilibrium favors the side with fewer moles of gas to decrease gas particle collisions. When pressure is decreased, - --equilibrium favors the side with more moles of gas to increase gas particle collisions. Equilibrium constant - --Kc = [C][D] / [A][B] K > 1 - --there are more products than reactants at equilibrium K < 1 - --there are more reactants than products at equilibrium. temperature, pressure, and/or concentration increase and/OR if enzymes or catalysts are present. - --reaction speed increases endothermic process that takes place spontaneously - --ÎEntropy > 0 and ÎEnthalpy > 0 neutral - --When the number of H+ ions in a solution equals the number of OH- ions (7) acid - --If we add a substance to water that increases the concentration of H+ ions (0-6) base - --If we add a substance to water that increases the concentration of OH- ions ( 8-14)
strong acids - --completely dissociate in water HA â H+ + A- in water [HA] = [H+] weak acids - --partially dissociate in water HA â H+ + A- in water [HA] â [H+] acid dissociation constant (Ka) - --calculated by dividing the concentration of the products, hydrogen ions and conjugate base, by the original concentration of the acid Kb - --calculated by dividing the concentration of the products, hydroxide ions and conjugate acid, by the original concentration of the base the weaker the acid - --the smaller the Ka and the less dissociation the weaker the base - --the smaller the kb and the less dissociation pH hydrogen ion - --pH = -log[H+] pH hydroxide - --pOH = -log[OH-] pH + pOH - -- arrhenius - --acids ionize in water(H+) ; bases ionize in water (OH-)
