Final Exam CHS 1440
How many grams of water can be produced if sufficient hydrogen reacts with 26.0 g of oxygen? 2 H2 (g) + O2 (g) -> 2 H2O (g)
(26.0 g O2) x (1 mol O2 / 32.0 g O2) x ( 2 mol H2O/ 1 mol O2) x (18.0 g H2O / 1 mol H2O) = 29.3 g H2O Answer: 29.3 g H2O
On the basis of your experience, predict which of the following reactions are spontaneous: (a) CO2(s) -> CO2(g) at 25 ºC (b) NaCl(s) -> NaCl(l) at 25 ºC (c) 2 NaCl(s) -> 2 Na(s) + Cl2(g) (d) CO2(s) -> C(s) + O2(g)
(a) CO2(s) -> CO2(g) at 25 ºC **SPONTANEOUS (b) NaCl(s) -> NaCl(l) at 25 ºC **NON-SPONTANEOUS (c) 2 NaCl(s) -> 2 Na(s) + Cl2(g) **NON-SPONTANEOUS (d) CO2(s) -> C(s) + O2(g) **NON-SPONTANEOUS
Which of the following hydrocarbons are isomers? 1. C6H14 2. C7H16 3. C6H14 4. C5H11OH 5. C6H14
1, 3, & 5
Chemical Changes
1. Burning Wood (Fire) 2. Iron rusting (Oxidation)
Physical Changes
1. Melting & Freezing 2. Boiling & Condensing 3. Dissolving
Example: Assuming the numbers given are measurements, carry out the indicated arithmetic operation and give the answer with the correct number of significant figures. 3.65 × 102 + 8.5 × 103 a) 12.15 × 10^2 b) 12.15 × 10^3 c) 8.9 × 10^3 d) 8.86× 10^3 e) 8.865 * 10^3
3.65 × 10^2 = 0.365 × 10^3 + 8.5 × 10^3 = 8.865 × 10^3 = 8.9 × 10^3 Answer: C
Use these two given reactions, 2 H2(g) + O2 (g) -> 2 H2O(g) ΔH = -483.6 kJ 3 O2(g) -> 2 O3(g) ΔH = +285.4 kJ to solve ΔHrxn for this reaction below: 3 H2(g) + O3(g) -> 3 H2O(g) ΔHrxn = ?
6 H2(g) + 3 O2 (g) -> 6 H2O(g) ΔH = -1450.8 kJ ( * 3 ) 2 O3(g) -> 3 O2(g) ΔH = -285.4 kJ ( * -1 ) 6H2(g) + 2O3(g) + 3O2 -> 6H2O(g) + 3O2 ΔHrxn = -1736.2 kJ ( / 2 ) 3H2(g) + O3(g) -> 3H2O(g) ΔHrxn = -868.1 kJ
Heats of Reaction for Some Specific Reactions
A formation reaction is the chemical reaction by which one mole of a compound is formed from its elements in their standard states. 8C(s; graphite) + 9H2 (g) -> C8H18 (liq) Fractional coefficients are allowed for formation reactions because only one mole of product can be formed. H2 (g) + Cl2 (g) -> 2HCL (g) 1/2 H2 (g) + 1/2 Cl2 (g) -> HCL (g) The standard state is the most stable form of an element at room temperature, 25°C, and pressure, 1 atm, indicated with a superscript °.
Spontaneity
A spontaneous process takes places without continuous intervention. Spontaneous processes are not necessarily rapid processes ( TIME IS NOT A FACTOR) C(diamond) -> C (graphite **Very slow, Spontaneous reaction Some spontaneous reactions only occur once they're initiated. The combustion of gasoline is a spontaneous reaction but only occurs when the reaction is initiated with a spark. Nonspontaneous reactions only occur with a continual input of energy.
Energy and Stoichiometry
A thermochemical equation allows for the stoichiometric treatment of energy. The thermochemical equation is used to convert between the number of moles of a reactant or product and the amount of energy released or absorbed. The stated value of ΔH for a thermochemical equation corresponds to the reaction taken place exactly as written, with the indicated numbers of moles of each substance reacting. 2 SO2 (g) + O2 (g) -> 2 SO3 (g) ΔH= -197.0 kJ 2 moles ΔH= -197.0 kJ 1 moles ΔH= -98.5 kJ
Condensed Phases - Solids
A unit cell is the smallest collection of atoms that displays all the features of the crystal structure. Three types of cubic unit cells: simple cubic (sc) containing 1/8 each of 8 corner atoms, body-centered cubic (bcc) containing one additional atom within, face-centered cubic (fcc) with an additional 1/2 each of 6 atoms along the faces.
Functional Groups
Arrangements of atoms that tend to display similar chemical properties. Chemical formulas are often written to emphasize functional groups. *Methanol, an alcohol, is often written CH3OH instead of CH40 Hydrocarbons contain ONLY H and C atoms Addition of functional groups to hydrocarbons results in more complex compounds
Atomic Number and Mass Number
Atomic Number, Z., is the number of protons in a nucleus. (Identifies the element) Mass Number, A, is the sum of the number of protons and number of neutrons in a nucleus. (A = proton + neutron)
Atomic Structure and Mass
Atoms have a nucleus which contains protons and neutrons. The nucleus is surrounded by a cloud of electrons. Most of the atom's mass (proton; neutron) & its positive charge (proton) are in the nucleus Most of the volume of the atom is empty space. Tiny, negatively charged electrons are dispersed in it. **The number of negatively charged electrons = number of positively charged protons The atom is electrically NEUTRAL
Q. Write a balanced chemical equation describing the reaction between butane (C4H10) and oxygen (O2) to form carbon dioxide and water.
C4H10(g) + O2 (g) CO2 (g) + H2O (g) BALANCE C C4H10(g) + O2 (g) 4CO2 (g) + H2O (g) BALANCE H C4H10(g) + O2 (g) 4CO2 (g) + 5H2O (g) BALANCE O C4H10(g) + 6.5O2 (g) 4CO2 (g) + 5H2O (g) Answer: 2C4H10(g) + 13O2 (g) 8CO2 (g) + 10H2O (g)
What is the molecular formula of the following compound?
C8H10O
Which type(s) of intermolecular forces need to be overcome to convert each of the following liquids to gases? CH4 (CH3)2CO CH3OH
CH4: Dispersion (CH3)2CO: Dispersion, dipole-dipole CH3OH: Dispersion, dipole-dipole, H-bonding
Organic Chemistry
Carbon compounds can become quite large, organic compounds are described simply and unambiguously using LINE STRUCTURES, where carbons and hydrogens are not explicitly shown. *Each corner or end of a line is a carbon * Hydrogen atoms on carbon atoms are implied. Carbon makes four bonds, "missing" bonds go to hydrogen atoms. Hydrogen can only make one covalent bond to another atom *Hydrogen atoms on any other element are shown *All other elements are shown
History and Application of the Ideal Gas Law
Charles's Law: T = V See Attachment Boyle's Law: P = 1 / V P1V1 = P2V2 Avogadro's Law: n = V (V1/n1) = (V2/n2) The empirical gas laws led to the ideal gas law. PV = nRT
Which of the following represent(s) a chemical change? 1. Rusting of an Iron Bridge 2. Melting of Ice 3. Burning of a wooden stick 4. Digestion of a baked potato 5. Dissolving of sugar in water
Chemical - Rusting of an Iron Bridge Physical - Melting of Ice Chemical - Burning of a wooden stick Chemical - Digestion of a baked potato Physical - Dissolving of sugar in water Answer: 1, 3, and 4
Partial Pressure
Dalton's law of partial pressures: The total pressure (P) of a mixture of gases is the sum of the partial pressures of the component gases (Pi). Daltons Law can be expressed in terms of mole fraction. Mole fraction (Xi) for a gas in a gas mixture is the moles of the gas (ni) divided by the total moles of the gases present. The partial pressure of each gas is related to its mole fraction.
Chemical Properties
Determined only by observing how a substance changes its identity in chemical reactions. Examples: Oxidizing-reducing (Corrosion), Flammability, & Explosiveness
Heat Capacity and Calorimetry
Different systems will absorb different amounts of energy based on three main factors. The amount of material, m or n. m is mass and n is number of moles The type of material, as measured by c or Cp. c is the specific heat capacity, or specific heat, and Cp is the molar heat capacity. The temperature change, ΔT.
Hee's Law and Heats of Reaction
Direct calorimetric determinations of some reactions may be too difficult or dangerous to perform. An indirect method is needed to obtain heats of reaction. Hess's law: the enthalpy change for any process is independent of the particular way the process is carried out. Enthalpy is a state function. A state function is a variable whose value depends only on the state of the system and not its history.
Semiconductors
Electrical conductivity of semiconductors can be modified via doping. Doping - adding trace amounts of an element to a substance to modify its properties. n-type: prepared by doping with a valence electron rich element; "negative" p-type: prepared by doping with a valence electron deficient element; "positive" Doping Si with Al means the dopant has fewer than 4 valence electrons (holes).
Hee's Law
Enthalpy diagram for the combustion of methane. The CH4 is converted to CO, then the CO is converted to CO2. The ΔH for each step is used to calculate the ΔH for the overall reaction. The ΔH will be the same for both paths.
Entropy
Entropy can be tentatively defined as a measurement of the randomness, or disorder, of a system. Certain types of changes will result in increased entropy. Certain phase changes. Solid (Melting) -> Liquid (Boiling) - > Gas **-> (Entropy Increases) An increase in the number of particles present. C3H8(g) + 5 O2(g) -> 3 CO2(g) + 4 H2O(g) **ENTROPY INCREASES CO(g) + 2 H2(g) -> CH3OH(l) **ENTROPY DECREASES An increase in the temperature of a substance.
Ideal Gas Law
Equation: PV = nRT The ideal gas law is the quantitative relationship between pressure (P), volume (V), moles gas present (n), and the absolute temperature (T). R is the universal gas constant. R = 0.08206 L atm mol-1 K-1: used in most gas equations (universal gas constant)
Temperature Scale Conversions
F = (1.8 x C) + 32 C = (F-32) / 1.8 K = C + 273.15 C = K - 273.15
Determination of the Rate Law
For a reaction with only one reactant, A, the rate of the reaction is rate = k[A]n. The common possible orders with respect to A are 0, 1, 2. If the concentration of A is doubled experimentally, the rate of the reaction will change in a simple and predictable way. If n = 0, doubling [A] does not change the reaction rate. If n = 1, doubling [A] doubles the reaction rate. If n = 2, doubling [A] quadruples the reaction rate. For a reaction with two reactants, A and B, the rate of the reaction is rate = k[A]m[B]n. To separate the influence of one reactant concentration from the other, one reactant concentration is held constant while changing the other to determine its effect on the rate. To determine the order with respect to A and B, at least three experiments must be carried out.
Significant Figures in Calculations
For calculated values, the number of significant figures should be consistent with the data used in the calculation
Stoichiometry of Reactions Involving Gases
For reactions involving gases, the ideal gas law is used to determine moles of gas involved in the reaction. Use mole ratios (stoichiometry) Connect number of moles of a gas to its temperature, pressure, or volume with ideal gas law PV=nRT
Solution Stoichiometry
For reactions occurring in solution, the concentration and volume of reactants and products are often used instead of mass to solve solution stoichiometry problems. **Moles can be solved from concentration (molarity) and volume (Liters) ** moles = Molarity (M) X Volumer (L)
Electron Configuration
For silicon (14 electrons) 14Si: 1s2 2s2 2p6 3s2 3p2 14Si: [Ne] 3s2 3p2 Orbitals Fill in the Following Order: 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p
Nitrogen
Forms a number of binary compounds with oxygen N2O = Dinitrogen Monoxide NO = Nitrogen Monoxide NO2 = Nitrogen Dioxide N2O3 = Dinitrogen Trioxide N2O4 = Dinitrogen Tetroxide N205 = Dinitrogen Pentoxide
Hybrid Orbitals
Hybrid orbital name comes from the type and number of atomic orbitals combined (e.g., sp3) The indicated orbital geometry gives rise to common molecular shapes.
Limiting Reactant
In many chemical reactions, one reactant is often exhausted before the other reactants. This reactant is the LIMITING REACTANT Limiting reactant is determined using stoichiometry. The limiting reactant limits the quantity of product produced.
Intermolecular Forces
Intermolecular forces - the attractive and repulsive forces between molecules. Dispersion forces are common to all molecules (NO, Ne). ****Also referred to as instantaneous dipole-induced dipole forces. Dipole-dipole forces are the attractive and repulsive forces for molecules with a permanent dipole. Hydrogen bonds are a special case of dipole-dipole forces. ****Hydrogen bonds occur only in compounds containing hydrogen covalently bonded to the highly electronegative elements F, O, or N.
Naming Ionic Compounds
Ionic compounds are electrically neutral and are named in order of "cation anion", as in sodium chloride. The cation retains its full name. Monoatomic cation charge can often be found by position in the periodic table. Cations with more than one charge (e.g., transition metals) are named using Roman numerals indicating the charge, e.g., iron(II) Monatomic anions are named by replacing the ending of the element name with the suffix -ide, e.g., bromide A polyatomic cation or anion is named using its common name. *lead(IV) oxide PbO2
The Macroscopic Perspective
Matter is anything that has mass and can be observed Matter is observed through physical and chemical changes
Temperature
Measured using the Fahrenehit, Celsius, and Kelvin (absolute) scales
Acid-Base Reactions
Mixing an acid and a base leads to a reaction known as neutralization, in which the resulting solution is neither acidic nor basic. Net ionic equation for neutralization of strong acid and strong base.
Ratios from a Balanced Chemical Equation
Mole ratios are obtained from the coefficients in the balanced chemical reaction. 1 CH4 : 2 O2 : 1 CO2 : 2 H2O 1 mol CH4: 2 mol O2 : 1 mol CO2 : 2mol H2O These ratios can be used in solving problems
Chemical Equations for Aqueous Reactions
Molecular Equation: AgNO3(aq) + NaCl(aq) = AgCl(s) + NaNO3(aq) Total Ionic Equation: Ag+(aq) + NO3-(aq) + Na+(aq) + Cl-(aq) = AgCl(s) + NO3-(aq) + Na+(aq) Net Ionic Equation: Ag+(aq) + Cl-(aq) = AgCl(s) Spectator Ions: Are ions uninvolved in the chemical reaction ** Spectator ions: NO3- and Na+ **
Shapes of Molecules
Molecular shapes for various combinations of bonding and nonbonding electron pairs.
Addition & Subtraction
Number of sig figs are determined from the position of the FIRST UNCERTAIN DIGIT 3.65 x 10^2 m + 8.1 x 10^3 m = 8.5 x 103 m
Chemical Bonds and the Structure of Molecules
Octet rule - an atom will form covalent bonds to achieve a complement of eight valence electrons. The valence shell electronic configuration is ns2np6 for a total of eight electrons. Lewis dot symbols keep track of valence electrons, especially for main group elements, allowing prediction of bonding in molecules. To draw a Lewis dot symbol, the valence electrons are represented by dots and are placed around the element symbol. The first four dots are placed singly. Starting with the fifth dot, they are paired.
Electron Configuration
Pauli Exclusion Principle: no more than two electrons can occupy any orbital Hund's rule: Fill a set orbitals of same energy with electrons singly, with parallel spins, before pairing starts. Aufbau Principle: Lower-energy orbitals fill before higher-energy orbitals.
Which of the following properties of a metal are chemical properties? 1. It is hard 2. It rusts in air 3. Its density is 5.5 g/cm^3 4. It reacts with a base 5. It is a good electrical conductor
Physical - It is hard Chemical - It rusts in air Physical - Its density is 5.5 g/cm^3 Chemical - It reacts with a base Physical It is a good electrical conductor Answer: 2 & 4
An engine generates 15.7 g of nitric oxide gas during a laboratory test. How much heat was absorbed in producing this NO? N2 (g) + O2 (g) -> 2 NO (g) ΔH= 180.5 kJ
Ratio to use: 2 mole NO need 180.5 kJ n= m x 1/Mno 15.7 g x 1/30.0 g n= 0.523 mol 0.523 mol x 180.5 kJ / 2 mol = 47.2 kJ
Theoretical and Percentage Yields
Reaction efficiency is measured with percentage yield. The mass of product obtained is the actual yield. The ideal mass of product obtained from calculation is the theoretical yield.
If a 5.0 L flask holds 0.125 moles of nitrogen at STP, what happens to the entropy of the system upon heating the gas to 75 °C?
The Entropy Increases
Gibbs Free Energy
The Gibbs free energy function, G, is defined as: G = H - TS Changes in this function can predict whether or not a process is spontaneous under conditions of constant pressure and temperature. ΔG = ΔH - TΔS ΔG<0 Spontaneous
The Rate Law
The experimentally determined exponents (m, n) are referred to as the order of the reaction. If m = 0, the reaction is said to be zero order. If m = 1, the reaction is said to be first order. If m = 2, the reaction is said to be second order. Exponents greater than 2 are unusual. For reactions where the rate depends on more than one reactant concentration: The exponent on each reactant is the order with respect to that reactant. The sum of the exponents (m + n) is the overall order of the reaction.
Naming Covalent Compounds
The first element in the formula retains is full name. The second element is named by replacing the ending from its name with the suffix -ide. Both elements are preceded by a number-designating prefix except when there is only one atom of the first element, which will not use the prefix mono-.
Breaking of the Ideal Gas Law
The ideal gas model breaks down at high pressures and low temperatures. high pressure: volume of particles no longer negligible low temperature: particles move slowly enough to interact
Balancing Chemical Equations
The law of conservation of matter: matter is neither created nor destroyed. Chemical reactions must obey the law of conservation of matter. The same number of atoms for each element must occur on both sides of the chemical equation. A chemical reaction simply rearranges the atoms into new compounds. Chemical equations may be balanced via inspection, which really means by trial and error. Numbers used to balance chemical equations are called stoichiometric coefficients. The stoichiometric coefficient multiplies the number of atoms of each element in the formula unit of the compound that it precedes. Stoichiometry is the various quantitative relationships between reactants and products.
Theoretical Yield
The maximum mass of a product that can be obtained in a reaction is determined by the limiting reactant. Determine which reactant is the limiting reactant. Calculate the mass of product that can be made from the limiting reactant. This mass is the theoretical yield. In stoichiometric mixtures, however, both reactants are consumed completely, so either could be considered the limiting reactant.
Multiplication & Division
The number of sig figs in a result must be the same as the number of sig figs in the factor with the FEWEST sig figs! 0.24 kg x 4621 m = 1100 kg m or 1.1 x 10^3 kgm
Formation of Ions
The potential energy, V, for the ion pair can be calculated. V = k (q1q2) / (r) k = 1.389 x 105 kJ pm/mol The lattice energy is the overall result of the potential energy between the ions in a crystal. Small ions with large charges form ionic compounds with large lattice energies. Large ions with small charges form ionic compounds with small lattice energies
Dilution
The process in which solvent is added to a solution to decrease the concentration of the solution The number of the moles of solute is the same before and after dilution Since the number of moles of solute equals the product of molarity and volume (M X V), we can write the following equation, where the subscripts denote initial and final values. Mi X Vi = Mf x Vf
Second Law of Thermodynamics
The second law of thermodynamics: in any spontaneous process, the total entropy change of the universe is positive (ΔSu > 0); entropy increase. ΔSu = ΔSsys + ΔSsurr ΔSu = entropy of the universe ΔSsys = entropy of the system ΔSsurr = entropy of the surroundings It is impossible to convert heat completely to work, since work is a process that involves moving random motions into more ordered ones.
Free Energy and Chemical Reactions
The standard Gibbs free energy change, ΔGº, can be calculated from Gibbs free energies of formation, ΔGfº. ΔGfº = 0 for elements in their free standard state. ΔGfº = Sum vi ΔGfº (products) i - Sum vj ΔGfº (reactants) j ΔHrxnº = Sum vi ΔHfº (products) i - Sum vj ΔHfº (reactants) j This equation provides an alternative method to calculate ΔG, without entropy or enthalpy.
Inorganic and Organic Chemistry
The study of the compounds of the element carbon, usually with oxygen, nitrogen and hydrogen. Isomers: Different organic molecules that have the same formula but are connected differently Inorganic Chemistry - Is the study of ALL other elements and their compounds
Ratios from a Balanced Chemical Equation
This flow diagram illustrates the various steps involved in solving a typical reaction stoichiometry problem. No different than unit conversion Usually more than one conversion is necessary Write all quantities with their complete units Mass Given (Grams) -> Molar Mass RATIO -> Moles In -> Balanced Chemical Equation (RATIO) -> Moles out -> Molar Mass (RATIO) -> Mass Desired (Grams)
Calculation of Packing Efficiency
To determine the number of complete atoms per unit cell: fcc = 1/2 (# face-center atoms) + 1/8 (# corner atoms) = 4 bcc = (# body-center atoms) +1/8 (#corner atoms) = 2 sc= 1/8 (# corner atoms) =1 To find the total volume occupied by atoms: r is the radius. Total volume occupied by atoms = # atoms in unit cell x (4/3 pi r ^3)
Calculation of Packing Efficiency
To find the volume of the unit cell in terms of radius: V = a^3 (where a is the edge length of the unit cell) a(fcc) = (2sqrt2) r a(bcc) = (4 / sqrt3) r a(sc) = 2r To calculate packing efficiency: Packing efficiency = ( (Volume of atoms in unit cell) / (Total volume of unit cell) ) x 100
Determine the initial volume needed to generate 2.50 L of 1.50 M H2SO4 from 3.75 M H2SO4 by dilution. a) 2.50 L b) 1.00 L c) 1.50 M d) 1.50 L e) 92.6 mL
Use Mi X Vi = Mf X Vf Mf = 1.50 M; Vf = 2.50 L Mi = 3.75 M; Vi = ? Vi = (Mf X Vf) / (Mi) =1.00 L b) 1.00 L
Vapor Pressure
Vapor pressure - the gas phase pressure of a substance in dynamic equilibrium with the pure liquid in a pure substance. Vapor pressure is a characteristic property of a particular substance at a particular temperature. ****Liquids with strong intermolecular forces have lower vapor pressures (cooking oil; motor oil). Liquids with weak intermolecular forces have higher vapor pressures & are described as volatile (formaldehyde).****
Physical Properties
Variables of matter that we can measure without changing the identity of the substance being observed. Examples: Color, Luster, Solubility, Size, Hardness, Conductivity, Odor, Condensing, Boiling Point, Density & Melting Point
Without doing a calculation, predict the entropy change of these process? a) 2 HNO3(l) + NO(g) -> 3 NO2(g) + H2O(l) b) FeCl2(s) + H2(g) -> Fe(s) + 2HCl(g) c) CO(g) +2 H2(g) -> CH3OH(l) d) 2H2O(g) -> 2H2(g) + O2(g) e) 2H2(g) + O2(g) -> 2H2O(l)
a) 2 HNO3(l) + NO(g) -> 3 NO2(g) + H2O(l) **INCREASE** b) FeCl2(s) + H2(g) -> Fe(s) + 2HCl(g) **INCREASE** c) CO(g) +2 H2(g) -> CH3OH(l) **DECREASE** d) 2H2O(g) -> 2H2(g) + O2(g) **INCREASE** e) 2H2(g) + O2(g) -> 2H2O(l) **DECREASE**
For which of the following is ΔHfº = 0; ΔGfº = 0? a) Al(g) b) MgCO3(aq) c) C (graphite) d) Cl2(g) e) CO2(g)
a) Al(g) **NOT THE STANDARD STATE** b) MgCO3(aq) **NOT AN ELEMENT** c) C (graphite) **THE STANDARD STATE** d) Cl2(g) **THE STANDARD STATE** e) CO2(g) **NOT AN ELEMENT**
Q. Predict the order of increasing vapor pressure for the following compounds. a) FCH2CH2F b) HOCH2CH2OH c) FCH2CH2OH
a) FCH2CH2F *Weakest IMFs highest VP *dispersion dipole-dipole b) HOCH2CH2OH *Strongest IMFs lowest VP *dispersion dipole-dipole H-bonding c) FCH2CH2OH *dispersion dipole-dipole H-bonding (less) Answer: Order of increasing Vapor Pressure: b < c < a
Choose the compound below that should has the largest lattice energy. a) MgO b) CaO c) NaF d) MgS e) KF
a) MgO Mg2+ < Ca2+ a) MgO > b) CaO O2- < S2- a) MgO > d) MgS Na+ < K+ c) NaF > e) KF Mg2+ < Na+, O2- < F- a) MgO > c) NaF Small ions with large charges form ionic compounds with large lattice energies. Large ions with small charges form ionic compounds with small lattice energies.
Which of the following represents invalid set of quantum numbers? a) n = 3, l = 3, ml = 3, b) n = 2, l = 1, ml = 0, c) n = 3, l = 0, ml = 0, d) n = 4, l = 3, ml = 3, e) n =5, l = 1, ml = -1
a) n = 3, l = 3, ml = 3, n = 1, 2, 3, .... l = 0, 1, 2, n-1 ml = -l, ...0, ... l ms = ± 1/2
The sign of Hrxn and Srxn for several reactions are given. Determine the spontaneity of these processes. a) ΔHrxn < 0; ΔSrxn < 0 b) ΔHrxn < 0; ΔSrxn > 0 c) ΔHrxn > 0; ΔSrxn < 0 d) ΔHrxn > 0; ΔSrxn > 0 e) ΔHrxn = ΔSrxn
a) ΔHrxn < 0; ΔSrxn < 0 ** SPONTANEOUS AT LOW TEMP** b) ΔHrxn < 0; ΔSrxn > 0 ** ALWAYS SPONTANEOUS** c) ΔHrxn > 0; ΔSrxn < 0 ** ALWAYS NONSPONTANEOUS** d) ΔHrxn > 0; ΔSrxn > 0 ** SPONTANEOUS AT HIGH TEMP**
The correct formula for iron(II) chloride is: a) FeCl b) FeCl2 c) FeCl3 d) Fe2Cl e) Fe2Cl2
b) FeCl2
What is the net ionic equation for the reaction between aqueous sodium hydroxide and aqueous nitric acid? a) H+(aq) + NaOH(aq) → H2O(l) + Na+(aq) b) H+(aq) + OH-(aq) → H2O(l) c) HNO3(aq) + NaOH(aq) → H2O(l) + NaNO3(aq) d) Na+(aq) + NO3-(aq) → NaNO3(aq) e) HNO3(aq) + OH-(aq) → H2O(l) + NO3-(aq)
b) H+(aq) + OH-(aq) → H2O(l)
Choose the substance that corresponds to an n-type semiconductor a) As doped with Si b) Si doped with P c) Si doped with Al d) Sn doped with Ga e) P doped with Ge
b) Si doped with P
Write the ground state electron configuration for manganese. a) [Ar] 4s24p5 b) [Ar] 4s23d5 c) [Ar] 3d7 d) [Ar] 3d54p2 e) [Kr] 4s23d5
b) [Ar] 4s23d5 Orbitals Fill in the Following Order: 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p 25Mn: 1s2 2s2 2p6 3s2 3p6 4s2 3d5 [Ar] 4s2 3d5
How many protons, neutrons, and electrons are in the 25Mg atom? a) 25 protons, 0 neutrons, 25 electrons b) 12 protons, 13 neutrons, 13 electrons c) 12 protons, 13 neutrons, 12 electrons d) 13 protons, 12 neutrons, 13 electrons e) 12 protons, 25 neutrons, 12 electrons
c) 12 protons, 13 neutrons, 12 electrons Z = 12 A = 25 (A-Z) = 13
How many valence electrons are in carbon? a) 1 b) 2 c) 4 d) 6 e) 8
c) 4 6C Orbitals Fill in the Following Order: 1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p 6C: 1s2 2s2 2p2
At constant temperature, 14.0 L of O2 at 2.70 atm is compressed to 5.35 L. What is the final pressure of O2? a) 0.110 atm b) 0.142 atm c) 7.06 atm d) 21.6 atm e) 27.8 atm
c) 7.06 atm P1 = 2.70 atm V1 = 14.0 L V2 = 5.35 L Equation P2 = (P1V1 / V2) ((2.7)(14) / (5.35)) P2 = 7.06 atm
What's the packing efficiency of the face-centered cubic structure? a) 52% b) 68% c) 74% d) 78.5% e) 90.7%
c) 74%
Which of the following compounds illustrates sp3 hybridization? a) C2H4 b) BeF2 c) CH4 d) V2O5 e) SO2
c) CH4
Explain why the following is not a formation reaction. 4Na(s) + O2(g) -> 2Na2O(s) a) The standard state of oxygen is O(g). b) The equation is not balanced. c) Two moles of the compound are formed. d) Gases can only be on the product side. e) The product is not an element.
c) Two moles of the compound are formed.
Give the name of the following compound: N2O5 nitrogen oxide b) dinitrogen oxide c) dinitrogen pentoxide d) nitrogen pentoxide e) nitrogen oxygen
c) dinitrogen pentoxide
In assembling a Lewis Dot diagram of PO43-, there are ____ total electrons to use in the model. a) 50 b) 48 c) 40 d) 32 e) 29
d) 32 P: 1 x 5 = 5 O: 4 x 6 =24 +3 extra e- = 3 Total = 32 Lewis dot symbols keep track of valence electrons, especially for main group elements, allowing prediction of bonding in molecules.
A particular orbital has n = 4 and l = 2. What must this orbital be? a) 3p b) 4s c) 4p d) 4d e) 5s
d) 4d
The combustion of methane (CH4) produces carbon dioxide (CO2) and steam (H2O). All of the following statements concerning this reaction are correct EXCEPT a) one molecule of carbon dioxide is formed per one molecule of methane consumed. b) two molecules of oxygen are consumed per one molecule of methane consumed. c) two moles of steam are formed per two moles of oxygen consumed. d) the combined mass of reactants consumed equals the mass of products formed. e) 1 gram of carbon dioxide are formed per two grams of oxygen consumed.
e) 1 gram of carbon dioxide are formed per two grams of oxygen consumed.
Which of the following is an example of an alcohol? CH3CHO b) CH3OCH3 c) CH3COOH d) NH3OH e) CH3OH
e) CH3OH
Which of the following relationships are true for gases? i) The number of moles of a gas is inversely proportional to its volume (at constant pressure and temperature). ii) The pressure of a gas is directly proportional to its temperature in kelvins (at constant volume). iii) The volume of a gas is inversely proportional to its pressure (at constant temperature).
i) The number of moles of a gas is inversely proportional to its volume (at constant pressure and temperature). FALSE ii) The pressure of a gas is directly proportional to its temperature in kelvins (at constant volume). TRUE iii) The volume of a gas is inversely proportional to its pressure (at constant temperature). TRUE
Quantum Numbers
m = Principle Quantum Numbers - Shell l = Secondary Quantum Number = Subshell ml = Magnetic Quantum Number - Subshell Direction ms = Spin Quantum Number - Spin direction n = 1,2,3,.... l= 0,1,2,n-1.. ml= -l,...0,...l ms= +- 1/2 1s s: Secondary quantum number (l) *Indicates the subshell of the orbital 1: (Principal Quantum Number (n). *Indicates the principal shell of the orbital
Quantum Numbers
n = 1 is the first shell, n = 2 is the second shell, etc.
Copper wires used to transport electrical current heat up because of the resistance in the wire. If a 140 g wire gains 280 J of heat, what is the change in temperature of the wire? Specific heat of Cu = 0.384 J/goC
q=mcΔT ΔT = q/mc = 280 J / (140 g * 0.384 J/gC) =5.2 C
Question: Nitrogen boils at -320.4 F. What is this temperature in Kelvin?
ºC = (-320.4 - 32) / 1.8 = (-352.4) / 1.8 = -195.8 K = -195.8 + 273.15 = 77.4
Free Energy and Spontaneous Change
ΔG < 0 spontaneous ΔG > 0 nonspontaneous For a spontaneous reaction with a negative ΔH and a negative ΔS, the reaction only occurs at low temperature. ΔH < 0 ΔG = ΔH - T1ΔS = 0 ΔS < 0 ΔG' = ΔH - T2ΔS < 0 T2 < T1 For a spontaneous reaction with a positive ΔH and a positive ΔS, the reaction only occurs at high temperature. ΔH > 0 ΔG = ΔH - T1ΔS = 0 ΔS > 0 ΔG' = ΔH - T2ΔS < 0 T2 > T1
Confirm that the reaction below would be spontaneous, or nonspontaneous at 25oC, by calculating the standard free energy change, ΔGo, using values for ΔGfo. 2 C2H4 (g) + H2 (g) -> C4H1O (g)
ΔGof (kJ/mol) 2 C2H4 (g): 68.12 H2 (g): 0 C4H1O (g): -15.71 ΔGfº = ΔGfº ((C4H1O (g)) - 2ΔGfº ((C2H4 (g)) - ΔGfº (H2 (g)) = (-15.72 kJ) - 2 (68.12) - (0) = - 151.95 kJ ** REACTION IS SPONTANEOUS **
Confirm that the reaction below would be spontaneous, or nonspontaneous at 25 C, by calculating the standard free energy change using the values from ΔH and ΔS. ΔHrxn = -283.0 kJ ΔGrxn = ΔHrxn - TΔSrxn
ΔGrxn = -283.0 kJ - 298 K x (-86.6 J/ K) x (1 kJ/1000 J) = -283.0 kJ + 25.8 kJ =-257 kJ . Spontaneous reaction
When magnesium sulfite decomposes, the solid transforms into magnesium oxide and sulfur dioxide. MgSO3(s) → MgO(s) + SO2(g) At what temperature will this reaction be spontaneous according to Gibb's Energy?
ΔHfo in kJ/mol for: MgSO3(s) = −1068, MgO(s) = −601.8, SO2(g) = −296.8 So in J/mol K for: MgSO3(s) = 121, MgO(s) = 27, SO2(g) = 248.1
