MCAT Chemistry Flashcards
Cathode
A negatively charged electrode which attracts cations. Where reduction takes place.
How does a concentration change affect equilibrium?
If one of the substances is added or removed, all the concentrations of substances adjust to a new equilibrium with the same Keq
Electronegativity difference
A number found by taking the difference between the electronegativities of two atoms in a bond. Its value determines the type of bond.
List some basic facts about solutions
Particle size less than 1 mmicron; Clear (may be colored); Particles don’t settle; Can pass through membranes; Particles not visible
Endothermic Reaction: ΔH is (positive or negative); Enthalphy is (increased or decreased)
Positive; Increased
Atomic Mass Unit
the mass of a proton or neutron is equal to 1 atomic mass unit. Symbol - “amu”; 1 amu=1.66x10^-24
Hydrogen bonding
Formed when hydrogen is bonded to oxygen, fluorine, or nitrogen. The hydrogen of one molecule becomes attracted to the electronegative element of the other molecule. These intermolecular attractions cause higher boiling points than predicted
Phase equilibrium
For a liquid in a closed container, when the rates of evaporation (liquid to gas) and condensation (gas to liquid) equalize; the concentration of each is stable.
Emission Spectrum
A bright line spectrum formed when energy absorbed by an element is emitted at specific wavelengths. Each element has a unique spectrum.
Le Chatelier’s Principle
If stress is placed on a system at equilibrium, the equilibrium shifts in order the counteract the effects of the stress and regain equilibrium
in H2O solutions: 1) How many ˚C is the freezing point depressed for each molal of solute? 2) How many ˚C is the boiling point elevated for each molal of solute?
1) 1.86C for each molal of particles of solute; 2) 0.51C for each molal of particles of solute
Electrode Potential
A measure in volts of the tendency of atoms to gain or lose electrons. (Relative to a H2 oxidation reaction which has an assigned value of zero)
State the collision theory of reaction rates
There must be collisions between reactants. Reaction rate depends on number of collisions per unit time and the percent which are successful (Have sufficient energy)
Use conversion factors to solve: 1) How many kilograms in 2000 g? 2) How many feet in 60”?
1) (2000g)(1kg/1000g) = 2kg; 2) (60”)(1’/12”) = 5 ft
Describe the change in nonmetallic activity across the periodic table
Non-metallic activity increases across the table (L to R) and decreases down the columns
Molarity - general equation
The number of moles of solute it a liter of solution; M = n/L
Normality
The number of gram-equivalent weights in a liter of solution
Anode
A positively charged electrode which attracts anions. Where oxidation takes place.
Triple Point
The only temperature and pressure combination at which the 3 phases of a substance (solid, liquid, gas) can co-exist in equilibrium
Which sublevels are present in energy levels 1, 2, 3, and 4-7?
1: s; 2: s, p; 3: s, p, d; 4-7: s, p, d, f
Alkene
A series of hydrocarbons containing at least one double covalent bond (CnH2n)
How does a pressure change affect equilibrium?
Only in reactions where gases are involved. The reaction will shift to oppose pressure change, resulting in fewer moles of gas particles
Positive Ion: which elements tend to form them?
Metals tend to form positive ions by losing electrons (Na → Na+ e-)
What are the two driving forces that control reactions?
A drive towards increased entropy (disorder). A drive towards decreased enthalpy (lower heat content)
Dalton’s Law of Partial Pressures
In a gas mixture, the total pressure equals the sum of the partial pressures of each component. Ptotal = P1 + P2 + P3…
Oxidation
The loss of electrons (ex. Cumetal →Cu+2 +2e-
Bronsted Theory
An acid is a proton donor. A base is a proton acceptor.
Metals. List 6 characteristics
Solid (except Hg); malleable & ductile; conduct heat & electricity; shiny reflective & lustrous; lose e- to form cations; good reducing agents
STP
Standard temperature (0C or 273 K) and Standard Pressure (1 atm or 760 torr)
Scientific notation
A number expressed as Ax10B. “A” is between 1.00 and 9.99 and “B” is an integer.
What are the valences of the elements of families IA through VIIIA?
The valences of elements in groups IA - VIIIA are the element’s column number. For example, the valence of Na is 1; O is 6
Atomic Number: What are the atomic numbers of helium, hydrogen, carbon, oxygen?
The number of protons in the nucleus of an atom of an element. Helium-2; carbon-6; hydrogen-1; oxygen-8
Carboxylic Acid
A hydrocarbon containing the carboxyl functional group. (R-C(=O)-O-H)
Negative Ion: which elements tend to form them?
Non-metals form negative ions by gaining electrons (Cl +e- →Cl-)
List the names of the first four energy levels (or shells)
1 or K; 2 or L; 3 or M; 4 or N
Aromatic compounds
Unsaturated ring structures with six carbon atoms. Benzene is the simplest aromatic. (CnH2n-6)
Beta particle
An electron ejected from the nucleus when a neutron decays to a proton; Increases atomic number by one; High velocity; Low energy
pOH. For what values is a solution acidic, basic, neutral?
pOH = -log[OH-]; The degree of basicity of a solution. 7=acid.
Coordinate covalent bond
When both electrons in a covalent bond are supplied by one atom
Electrolyte (give 3 examples)
A solute whose aqueous solution contains ions and conducts electricity (acids, bases, salts)
What is the order for filling sublevels (aufbau process) from lowest to highest energy
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d
For any substance, write a general formula to convert from Number of Particles to Moles
n = P/6.02x1023; n = number of moles; P = number of particles
Isotope
Atoms which contain the same numbers of protons but different numbers of neutrons (ex. Hydrogen has 3 isotopes with mass numbers of 1,2,3)
List names for alkanes with 1 to 10 carbons in a molecular chain
1 methane; 2 ethane; 3 propane; 4 butane; 5 pentane; 6 hexane; 7 heptane; 8 octane; 9 nonane; 10 decane
Endothermic
A chemical reaction which absorbs heat
Double replacement
A reaction where two ionic substances “trade” anions; NaCl + AgNO3 ↔ NaNO3 + AgCl
Second Law of Thermodynamics
The entropy of the universe increases for any spontaneous process.
Atomic Mass
A weighted average mass of the atoms of an element (assuming the carbon-12 isotope is exactly 12) (ex. Atomic mass of C=35.45 is calculated from two isotopes. Cl-35 and Cl-36)
Ion (provide examples)
An atom or group of atoms which contains a positive or negative electrical charge (ex. Na+; Cl-; SO4^2-)
Explain the rules for dividing the numbers in scientific notation
Divide the first numbers and subtract the exponents. (8x10^6)/(2x10^10) = 4x10^-4
Electronegativity
The ability of an atom to attract to itself the e- in a covalent bond. Values range from 0.7 (Cs) to 4.0 (F)
Six common characteristics of acids
Form H2O solutions; Conduct electricity; React with active metals; Turn blue litmus red; Neutralize bases; Sour taste
Fission
The breakdown of heavy nuclei into lighter nuclei. The source of nuclear power
Diatomic; list 7 diatomic elements found in nature
A molecule composed of two atoms. H2, N2, O2, Cl2, F2, Br2, F2, I2
Specific Heat. Give value for liquid water in calories and joules.
The amount of heat required to raise one gram of substance 1C. Water: 1cal/g-C or 4.18 J/g-C
For any substance, write a general formula to convert from Moles to Number of Particles
(n)(6.02x10^23) = P; n = number of moles; P = number of particles
Heat of Fusion (value for water)
The amount of energy required to change a gram of substance from solid to liquid at its melting point (water = 80 cal/g)
Non-metals. List 7 characteristics
1/2 are gases; solids are brittle; poor conductors of heat and electricity; dull & non-reflective; gain e- to form anions; good oxidizing agents
Transition element
A metal having two incomplete shells of electrons; many have multiple oxidation states; less active than family IA & IIA. Ex., Fe, Ag, Au, Cr, W
For any substance, write a general formula to convert from Moles to Grams
g=(n)(MM) where, n = moles MM = molecular mass g = grams
Valence electroncs
The electrons found in the outermost energy level of an atom
Solubility curves
A curve for a given substance which shows how much dissolves in a given amount of solvent at different temperatures.
Synthesis or combination
A reaction where 2 or more elements form a compound; N2 + 3H2 ↔2NH3; 2H2 + O2 ↔ 2H2O
Equilibrium
The point in a reversible reaction where the forward and reverse reactions are taking place at the same rate.
Oxidizing agent
A substance which causes another substance to be oxidized (oxidizing agent is simultaneously reduced)
Faraday
A unit of electric charge which deposits by electrolysis one equivalent weight of an element. Equals 96,500 coulombs
Electron configuration
The distribution of electrons into shells and sublevels for an atom of an element. Each element has a unique electron configuration.
What is a general rule for solubilities of polar and nonpolar compounds?
Like dissolves like; Ionic and polar solvents dissolve ionic, polar solutes (water dissolves salt). Non polar solvents dissolve nonpolar solutes (acetone dissolves gasoline)
Write the solubility product expression for AgCl ↔ Ag+ + Cl-
Ksp = [Ag+][Cl-]
Metallic Bonds
A sea of electrons surrounding positive metal ions
Physical properties
Properties which can be observed without changing the substance into something different. Color, odor, hardness, density, luster, state, conductivity, solubility, boiling and melting points
Compare the ionic radii of 1) Cl, S, P; 2) Na, Mg, Al; What is the reason for their different size?
1) Cl-1 is smallest; P-3 is largest (the P atom gained the most e-); 2) Na+1 is largest Al+3 is smallest (the Al atom lost the most e-)
Specific Rate Constant
Symbol is “k” in a rate equation. A constant specific to temperature and reaction which is part of every rate equation
Mole
6.02x10^23 items, can be anything. The number of atoms in one mole (atomic mass in grams) of a monoatomic element. The number of formula units in one mole (formula mass in grams) of an ionic compound. The number of molecules in one mole (formula mass in grams) of a molecular substance)
Amino Acid
Organic compounds which contain an amine and a carboxyl group. (H2N-CH(-R)-COOH)
Conjugate Base - Write conjugate base of HCl
When a Bronsted acid donates a proton, it becomes its conjugate base (conjugate base of HCl is Cl-)
Law of Multiple Proportions
The same elements may combine to form more than one compound. The ratios of atoms are in small whole numbers (H2O and H2O2)
Ionization energy
The energy change required for the removal of the outermost electron from the gaseous atom to form a +1 ion
Molecule
A group of two or more atoms held together by chemical bonds
Catalyst
a catalyst is introduced into a reaction to speed it up or slow it down. It is not consumed. An increase or decrease of activation energy results from an alternate reaction path.
Equivalent weight
The number of grams of an element which will accept or donate 1 mole of electrons
Write the equation to calculate the atomic mass of an element
Atomic mass of X = ((mx1)(%x1)/100%) + ((mx1)(%x1)/100%)) + etc.; mx1, mx2, mxN = atomic masses of each isotope of element; %x1, %x2, %xN = percent composition of each isotope
Dynamic equilibrium
In a closed container where opposing changes are taking place at equal rates; the concentration of all components remains constant.
Isomer
Compounds with the same molecular formula but different structural formulas (different connectivity)
Aldehyde
A hydrocarbon containing the aldehyde functional group (R-C(=O)-H)
List five factors that control reaction rate
nature of reactants; exposed surface area; concentrations; temperatures; presence of catalyst
Write the nuclear equation: 1) U238 loses an alpha particle; 2) Th234 loses a beta particle.
92U238 →90Th234 +2He4; 90Th234→ 91Pa234 + -1e0
Describe the change in electronegativity across the periodic table
Electronegativity tends to increase across the table left to right and decrease down the columns
Solvent (provide example
A substance, usually a liquid, into which another substance (solute) is dissolved. Water is the solven in iced tea.
List in the order of increasing enthalpy: solid, gas, liquid
Solid (least enthalpy) -> Liquid -> Gas (most enthalpy)
List four quantum numbers and their symbols
1) Principal energy level “n”; 2) sublevel “l”; 3) orbital “m1”; 4) spin “ms”
Octet Rule
Atoms tend to gain or lose outer shell electrons in order to achieve a noble gas configuration of 8 electrons
Single Replacement
A reaction involving the replacement ina compound of an element by another element. Zn + CuCl2 ↔ Cu + ZnCl2
Alcohol
hydrocarbons which contain the hydroxyl functional group (OH-) attached to a saturated carbon (R-O-H)
Mass number
The sum of protons plus neutrons n the nucleus of an atom
Nonelectrolyte (give 2 examples)
A solute whose aqueous solution does not conduct electricity (sugar, benzene, most organic compounds)
Alkyne
A series of hydrocarbons containing at least one triple covalent bond (CnH2n-2)
Seven common characteristics of bases
Form H2O solutions; Conducts electricity; Turns red litmus blue; Feels slippery; Caustic; Neutralizes acids; Bases + fats form SOAP
Vapor Pressure
The pressure the gas phase exerts on its liquid phase in a closed container. This pressure varies with temperature
Decomposition
A reaction where a compound breaks down into elements; CO2 ↔ C + O2; 2CaO ↔2Ca + O2
Write an equation to calculate energy change when a fixed mass of substance changes temperature
ΔH = mCpΔT, where ΔT = temperature change, Cp = Specific Heat; ΔH = heat absorbed or given off
How many grams of NaCl are required to prepare 500 grams of a 5% solution?
%Concentration = (gNaCl/gsolution)(100%); 5% =(x/500g)(100%);x=25 g NaCl
Alkane
A series of hydrocarbons with only single covalent bonds (CnH2n+2)
Conjugate Acid - Write conjugate acid of I-
When a Bronsted base accepts a proton it becomes its conjugate acid (conjugate acid of I- is HI)
Empirical Formula. What are the molecular and empirical formulas of peroxide?
An expression which gives the relative numbers of atoms of the elements in a molecule. Expressed as the lowest possible set of integers (H2O2, HO)
Quantum Number
A number used to describe the energy levels available to an electron. Each electron in an atom has a unique set of four.
Describe the change in atomic radius across the periodic table
The atomic radius tends to decrease from left to right across the table and increase down the columns
List some basic facts about suspensions
No brownian motion; Don’t pass through filter paper or a membrane; Cloudy but particles settle on standing; Particles visible with microscope or eye
Activation energy
The energy necessary for a reaction to begin. Obtained from the kinetic energy released during collision
Gay-Lussac’s Law of Combining Gas Volumes
When only gases are involved in a reaction, the volumes of reactants and products are in a small, whole number ratio.
Element. List some examples
A substance is composed of identical atoms. Gold, silver, oxygen, hydrogen, lead, chlorine, helium, iron, copper, fluorine, arsenic
Density: Write the general equation and three standard units
The mass of a unit volume of a substance. Density = mass/volume = g/mL; g/L; kg/L
List properties of ionic substances
Solids at 25C; Non-conducting as solids but conducting as aqueous solutions or liquids. Conducting as aqueous solutions or liquids. High melting & boiling points; Brittle; Low volatilities
List prefixes for naming hydrocarbons for 1-10 carbons in a molecule
1 meth; 2 eth; 3 prop; 4 but; 5 pent; 6 hex; 7 hept; 8 oct; 9 non; 10 dec
Nonpolar covalent bond
when the EN difference is very small (less than 0.5). Two bonded atoms share the valence e-. The resulting molecule has no electrostatic charge.
List three basic postulates of the bohr model for the hydrogen atom
1) e- are present only in specific energy states; 2) a quantum of energy is absorbed or emitted to change energy levels; 3) a quantum is the smallest amount of energy that can be gained or lost
How can ΔG be used to predict if a reaction is spontaneous?
When ΔG is positive it is not spontaneous; negative, it is spontaneous; equals 0 it is at equilibrium.
Half Reaction
One of the two parts, either the reduction or the oxidation, of an oxidation-reduction reaction
Write the equilibrium expression for aA + bB ↔ cC + dD
Keq = [C]^c[D]^d / [A]^a[B]^b, where Keq = Equilibrium constant
How can you determine if a redox reaction will take place spontaneously
Add the electrode potentials of the two half reactions. If the result is positive, the reaction is spontaneous; if negative, the reaction is not spontaneous.
Alpha particle
a helium nucleus; charge =+2; High energy; Low velocity; Ejection reduces atomic number by 2amu and atomic weight by 4amu
Fusion
The joining of lighter nuclei to form heavier nuclei. Source of the sun’s energy
Describe an ionic bond in terms of electronegativity difference
When the EN values differ by 1.7 or more. The atom with higher EN borrows the electrons from the atom with lower EN. The resulting positive and negative ions attract.
Thermochemical equation
A balanced chemical equation which includes the enthalpy change. (H2(g) +1/2O2(g) →H2O(l) ; ΔH = -285kJ
Conversion Factor
A fraction which expresses an equality between two units of measurement and can be used to convert from one to the other (ex. 1kg/1000g)
Free Energy Change (ΔG). Write the free energy equation.
A property which reflects a system’s capacity to do useful work. ΔG = ΔH - TΔS; G=free energy; S=entropy; H=enthalpy; T=kelvin
Polar covalent bond
When the EN difference is between 0.5 and 1.7, the bonding electrons stay closer to the more electronegative atom. Electrons are shared unequally.
Gram-equivalent weight
The amount of substance which reacts with or displaces 1 mole of H+ ions.
Compare potential energy and kinetic energy
Potential energy is energy due to position. KE is energy of motion.
Which three factors affect the rate of solubility?
Pulverizing; stirring; heating
Significant digits
Digits which are measured. All non-zero digits are significant. Zeros are significant unless they are placeholders
Resonance structures
Where there is more than one possible bonding structure in a molecule
Write conversion forumlas: 1) Celsius to Fahrenheit; 2) Celsius to Kelvin
1) ˚f = (1.8 x ˚celsius) + 32; 2) Kelvin = ˚celsius +273
Calculate the volume of 10M NaOH needed to titrate 5L of 2M HCl
MA x VA = MB x VB; 2M x 5L = 10M x VB; 1L = volume of base
What is the volume of 1 mole of any gas at STP?
22.4 L
Explain how to convert a number less than 1 to scientific notation
Move decimal point to right until only 1 digit remains to left. Indicate number of moves as a negative exponent of 10. (0.00356 = 3.56 x 10-3
Write the electron configuration for 1) Lithium; 2) Iron
1) 1s2, 2s1; 2) 1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d6
10 prefixes used to name covalent compounds
Mono=1; Di=2; Tri=3; Tetra=4; Penta=5; Hexa=6; Hepta=7; Octa=8; Nona=9; Deca=10
Addition reaction
In an unsaturated hydrocarbon, two atoms may be added to the structure across a double or triple bond (C2H2 + Br2 → Ch2Br2)
Substitution reaction. Which elements commonly substitute in alkanes?
A reaction where one of the hydrogen atoms in a hydrocarbon is replaced by another. Usually a halogen. (CH4 + Br2→Ch3Br + HBr
Saturated and Unsaturated. Which are sturated? Alkanes, alkenes, alkynes.
A compound only containing single covalent bonds is saturated. Alkanes are saturated. A compound containing double or triple bonds is unsaturated. Alkenes and alkynes are unsaturated.
Charles Law
V1/T1 = V2/T2 (pressure and amount of gas are constant; V=volume; T=Kelvin)
Hydrogenation
The process of adding hydrogen to an unsaturated hydrocarbon
How do temperature and pressure affect the solubility of a gas?
Solubility usually decreases with increasing temperature. Solubility increases in direct proportion to an increase in pressure.
Reactants; Products
1) The starting materials in a chemical reaction; 2) The substances formed in a chemical reaction
Column or Family
A verticle group of elements on the periodic table in the same column. They have similar properties and the same number of valence electrons.
Cycloalkane
An alkane which has a ring structure instead of a chain
Matter
A substance that occupies space has mass.
Hybrid orbitals (list three types)
Where 2 or more pure atomic orbitals are mixed to form identical hybrid orbitals (ex. Sp, sp2, sp3)
How are the concentrations of [H+] and [OH-] related in a solution?
The product of the concentrations = 1x10-14; [H+][OH-] = 1x10-14
The Law of Conservation of Mass
During a chemical reaction, matter is neither created nor destroyed
Avogadro’s Number
The number of atoms or formula units in “x” grams of an element or molecule where “x” is the atomic or molecular mass. (Always equal to 6.02 x 10^23)
Quantum
A packet of energy associated with a specific wavelength of electromagnetic radiation
Cation and Anion (provide examples)
cation - positively charged ion (Na+; Fe+2; NH4+; Ag+); anion - negatively charged ion (Cl-; SO4-2; OH-; P-3)
Ground State
Electron is at its lowest energy level as close to the nucleus as possible
Heat of Vaporization (value for water?)
The amount of energy required per gram to change a liquid to a gas at its boiling point (water = 540 cal/g)
List the names of the four sublevels and their electron capacities
sublevel s holds two electrons; p holds 6; d holds 10; f holds 14
Explain the rules for multiplying the numbers in scientific notation
Multiply the first numbers and add the exponents. (3x10^5)(2x10^3)= 6x10^8
pH. For what values is a solution acidic, basic and neutral?
pH = -log[H+] ; The degree of acidity of a solution. 7 = basic.
Energy
The ability to do work; it is released or absorbed during chemical reactions in the form of heat, light, electricity. (calorie, Joule: 1cal = 4.18J)
Solute (provide example)
The substance dissolved in another (solvent). Salt is the solute in salt water.
Write the equation for Percent Composition. What is the percent composition of Ca in CA(OH)2?
%=(me/FW)(100%); %= percent composition of the element; me=mass of element in one formula unit; FW = formula weight; (40/74)(100%) = 54% Ca in Ca(OH)2
For any substance, write a general formula to convert from Grams to Moles
n = g/MM; n = moles; MM = molecular mass; g = grams
Ether
A hydrocarbon containing an ether functional group. (R-O-R’)
Reducing agent
A substance which causes another substance to be reduced (reducing agent is simultaneously oxidized)
Solubility Product Constant (Ksp)
An equilibrium exists in a saturated solution between dissolved and undissolved solute. Ksp is the equilibrium constant for this reaction.
Exothermic reaction: ΔH is (positive or negative); Enthalphy is (increased or decreased)
Negative; Decreased
List some basic facts about carbon bonding
Carbon forms more compounds than any other element; Each atom requires 4 covalent bonds; Carbon can form long chains and rings; Bonds commonly to O, H, N, S, P, and halogens
How is the reaction rate related to concentration?
Reaction rate is directly proportional to the concentrations of reactants
Dehydrogenation
The process of removing hydrogen from a hydrocarbon
Calculate the molality of 10 moles of H2SO4 dissolved in a 4 kg of water
Molality = Moles Solute / kg solvent = 10/4 = 2/5 Molal
Chemical change
Where new substances are formed with new chemical and physical properties. Oxygen & hydrogen form water; sodium & chlorine form sale (sodium chloride)
Compound. List some examples
substance composed of two or more elements chemically combined. Water - H2O; Salt - NaCl; Sugar - C6H12O6; Ammonia - NH3
Forumlas and names of acids formed from: 1) F; 2) Cl; 3) Br; 4) I
1) HF - hydrofluoric acid; 2) HCl - hydrochloric acid; 3) HBr - hydrobromic acid; 4) HI - hydriodic acid
Enthalpy
The heat content of a system
Arhennius Theory
An acid yields protons in solution (H+ ions); A base yields hydroxide ions in solution (OH- ions)
Enthalpy change (state the equation)
The difference in heat content between the products and the reactants (ΔH = ΣHproducts - Σhreactants)
Write the general equation to calculate ΔH for a chemical reaction
ΔH = Σ(ΔHF-products) - Σ(ΔHF-reactants); where ΔHf = Heat of formation of reactants or products
Transmutation
The conversion of an element to a new element due to a change in number of protons. Ex. Alpha or beta decay
Compare primary and secondary alcohols
Primary: The OH- group is attaced to the end carbon of the chain. Secondary: The carbon bearing theOH- goup is directly attached to two other carbons.
Polymerization
The combination of two or more unsaturated molecules to form a larger chain molecule. This is how plastics are made.
Describe the change in metallic activity across the periodic table
Metallic activity decreases across the table (left to right) and increases down the columns
Physical change
Substance changes form or state only. Boiling, melting, freezing, dissolving, grinding, cutting
Exothermic
A chemical reaction which evolves heat
Are concentrations of product and reactant equal at equilibrium?
No. The are constant but not equal. Their relative concentrations are determined by the value of the equilibrium constant at that temperature.
Ideal Gas Law
PV = nRT, (P=pressure in atm; V = volume in L; n = # moles; R = 0.0820 Latm/Mol-K; T = Temp in K)
Amine
A hydrocarbon containing an amine functional group. (R-NH2)
Oxidation number
A number (positive or negative) representing the charge on an ion or atom involved in a chemical bond
Molar Heat of Formation
The molar heat of formation of a compound is equal to ΔH when 1 mold of compound is formed from its elements at 1 atm and 25C
Describe the shapes of the orbitals: 1) s; 2) p; 3) d; 4) f
1) s- sphere; 2) p - dumbbell shape with 2 lobes; 3) d - double dumbbell; most have 4 lobes; 4) f - most have 8 lobes
Molecular Mass
Found by adding all the atomic masses of an element. Ex. H2O. Molecular mass = 18; H2 = 2(1) O = 16
Compare Weight vs. Mass
Mass is the amount of matter. Weight measures gravitational force. Mass never varies. Weight can vary.
Three postulates of Dalton’s Atomic Theory
1) An element is composed of identical atoms; 2) Atoms of different elements have different properties; 3) Compounds are atoms of 2 or more elements chemically combined
Gamma radiation
Usually emitted with beta radiation; Has neither charge nor mass; High energy; Travels at the speed of light
In a thermochemical equation, what happens to ΔH when the moles of reactants double?
Enthalpy is directly proportional to mass. Therefore when the moles double, so does ΔH.
Molecular Formula. What is the molecular formula for ammonia?
An expression stating the number and kind of each atom present in a molecule of a substance (NH3 has 1 nitrogen atome and 3 hydrogen atoms in each molecule)
Homogeneous and Heterogeneous mixtures. Provide examples.
Homogeneous mixtures are uniform in composition (air, metal alloy, salt water). Heterogeneous mixtures are not uniform in composition (dirt, spaghetti sauce)
Write oxidation numbers for ions of: Group IA & IIA; Group VIA & VIIA
IA→+1; IIA→+2; VIA→-2; VIIA→-1
Ionization constant. Write the expression for the ionization of acid “HA”
For substances in solution that partially ionize. An equilibrium expression may be written with Ki; Ki = [H+][A-] / [HA]
How does a change in temperature affect equilibrium
The reaction shifts to a new equilibrium point with a new Keq. If the temperature is raised, the equilibrium is shifted to reaction which absorbs heat.