Chemistry Exam 1 Study Guide
Chemistry Exam 1 Study Guide 01:160:161
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This 15 page Study Guide was uploaded by nichl on Sunday October 2, 2016. The Study Guide belongs to 01:160:161 at Rutgers University taught by in Fall 2016. Since its upload, it has received 13 views. For similar materials see General Chemistry I in Chemistry at Rutgers University.
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Date Created: 10/02/16
General Chemistry Lecture 1 9/7/16 General Course Guidelines: Office hours: 12-6 PM Online recitations are available through: https://www-1.egyan.rutgers.edu/#/account/login Recitation Schedule: Dr. G. Govindarajoo o Email: email@example.com o Office hours: Monday 12:20-1:20 Hickman 131 Wednesday 12:35-1:35 Heldrich Science Building 204 Textbook: Chemistry Structure – Properties by Nivaldo Tro Exams: o Recitations Quiz = 5% o Exam Dates: October 15 9:40 – 11:00 pm November 2 9:40 – 11:00 pm December 7 9:40 – 11:00 pm Chapter 1 Notes: Definitions: o Chemistry: Study of composition, structure, and properties of matter and the changes that occur when matter interacts o Matter: Anything that has mass and occupies space o Atom: Smallest distinctive units of matter o Substance: a type of matter that has a definite or fixed composition that does not vary from one sample to another (e.g2 H O) o Element: A substance that cannot be broken down into simpler substances through a chemical reaction (e.g. He) o Compound: Substance made of two or more types of elements in fixed proportions (e.g. H2O) States of Matter: o Solid: Strongest attractions between particles, rigid shape, fixed volume o Liquid: Fixed volume, no fixed shape, free to move (fluid) o Gas: Weakest attra▯tio▯ ▯etwee▯ parti▯les, does▯’t ▯lu▯p together, ▯o fixed shape/volume Mixtures: General Chemistry Lecture 1 9/7/16 o No fixed composition or ratios o Homogeneous mixtures (solutions): Mixture that has the same composition and properties throughout the sample (i.e. a sugar water solution has same amount of sugar at top and bottom of a column) o Heterogeneous mixture: Varies in composition and/or varies in properties between different parts of the mixture (i.e. granite) Scientific method: o Hypothesis: Tentative explanation or prediction that must be testable by experimentation and create scientific data o Scientific data: provides patterns that can be summarized into scientific laws o Scientific Theory: Provides explanations for a natural phenomenon that can be tested by further experimentation Questions Findings Hypothesis Questions o Hypothesis and theories can be disproved by better tech, etc. Chemical reactions: Chemical change process that changes to composition of a material (i.e. burning gasoline) Law of Conservation of Mass: In a chemical reaction. Matter is neither created nor destroyed. Mass stays the same. Combined mass of reactants must equal combined mass of products Law of Definite Proportions: All samples of a given compound (pure) regardless of the source at preparation have the same proportion of their constituent elements Practice 1.1 Pg. 11 2 samples of Carbon Monoxide (CO) Sample 1 – 17.2g O + 12.9g C 17.2/12.9 = 1.33g O/1g C Sample 2 – 10.5g O + 7.8g C 10.5/7.8 = 1.3g O/1g C Suggested Problems: Ch. 1.1 – 1.7 # 35, 41, 49, 53, 59, 61 General Chemistry Lecture 2 9/8/16 Law of Multiple Proportions Whe▯ ▯ ele▯e▯ts ▯A+B▯ fo▯▯ ▯ diffe▯e▯t ▯o▯pou▯ds, the ▯asses of ele▯e▯t ▯B▯ ▯ith ▯g of ele▯e▯t ▯A▯ ▯a▯ ▯e e▯p▯essed as a ▯atio of s▯all ▯hole ▯u▯▯e▯s o Practice 1.2 Pg. 12: H + O form water and Hydrogen Peroxide. A sample of water decomposes to form 0.125g H to 1g O. A sample of Hydrogen Peroxide decomposes to form 0.0625g H to 1g O Steps to solve: Write out ratios for each compound: o Water: ▯.▯▯▯g H Hydrogen Peroxide: ▯.▯▯▯▯g H ▯g O ▯g O Take the ration of one compound over the other (usually larger number over the smaller number) Mass of H to ▯g O in Water ▯.▯▯▯ o Ratio:Mass of H to ▯g O in Hydrogen Pe▯.▯▯▯▯= ▯ In an instance where you do not get a whole number (integer) multiply numerator and denominator with integer until you get a whole number multiple Joh▯ Dalto▯’s Ato▯i▯ Theor▯ 1. Ea▯h ele▯e▯t is ▯o▯posed of ti▯▯, i▯dest▯u▯ti▯le pa▯ti▯les ▯alled ▯ato▯s▯ 2. All atoms of given element have the same mass and properties that differentiate them from other elements 3. Atoms combine in simple, whole number ratios to form compounds 4. Atoms of one element cannot convert to another element. Chemical reactions change only the way atoms are bound together with other atoms Cathode Rays Hi velocity electrons passed readily through highly evacuated tubes (vacuum tubes) Carriers of electric current were called cathode rays Observations 1. Rays are emitted from the cathode when electricity is passed through an evacuated tube 2. Rays are emitted in a straight line, perpendicular to the cathode surface 3. Rays cause glass and other materials to fluoresce 4. Rays are deflected by a magnet in direction expected for negatively charged particles (like charges repelled, beam deflected away from negatively charged particles because the beam – composed of electrons – is negative) 5. Composition of the cathode does not affect the properties of the cathode ray General Chemistry Lecture 2 9/8/16 *Do▯’t ▯eed dates fo▯ people o▯ othe▯ histo▯i▯al details, ▯e a▯e o▯l▯ ▯o▯▯e▯▯ed ▯ith the ▯esults of thei▯ 1 experiments J.J. Thomson Discovered electron (e ) o Negatively charged o Low mass o Found within all atoms Mass of cathode ray particle Charge of cathode ray particle ∗ ▯▯ −▯▯ in units of kilograms per Coulomb (kg/C) Cathode ray particle is the electron Coulo▯▯’s Law Like charges repel, unlike charges attract Millika▯’s Oil Drop E▯peri▯e▯t Found the fundamental unit of negative charge carried by an electron Charge of an electron: −▯.▯▯▯ ∗ ▯▯−▯▯C Value a▯o▯e ▯a▯ ▯e plugged i▯to Tho▯so▯’s e▯uatio▯ to fi▯d the ▯ass of o▯e ele▯t▯o▯ Mass of electron (me) −▯.▯▯ ∗ ▯▯ −▯▯] ∗ [▯.▯▯▯ ∗ ▯▯−▯9] = ▯.▯▯▯ ∗ ▯▯−▯▯ kg/e- Atomic Models Thomson thought positive charges were distributed evenly in a spherical cloud and electrons were arranged in the cloud in a manner where the attraction between negative and positive charges offsets the ▯epulsio▯ of the ▯egati▯e ▯ha▯ges. This is ▯alled the ▯Raisi▯/Plu▯ Puddi▯g Model▯ P▯o▯e▯ ▯▯o▯g ▯▯ Ruthe▯fo▯d’s ▯u▯lea▯ ▯odel of the ato▯ des▯▯i▯ed ▯elo▯ 1Class note said by professor General Chemistry Lecture 2 9/8/16 Rutherford’s E▯peri▯e▯t Bo▯▯a▯ded thi▯ ▯etal fil▯s ▯ith positi▯el▯ ▯ha▯ged alpha ▯α▯ pa▯ti▯les and found that some particles get deflected sharply as a result of a dense, positively charged nucleus while other particles pass straight through Nucleus Positively charged protons Neutral neutrons Account for nearly all of atomic mass. Electrons contribute nearly insignificant amount Charge of proton: ▯.▯▯▯ ∗ ▯▯▯9C Charge of electron: −▯.▯▯▯ ∗ ▯▯▯9 C Atom Neutral due to an equal number of protons and electrons Symbols: o Z – represents the atomic number (number of protons) o A – represents the mass number (sum of protons and neutrons) Isotopes: Elements with same number of protons but differing numbers of neutrons. Means that atoms of the same element may have different A values Ex: 17 protons, 17 electrons if neutral A-Z=neutrons 3Cl - 18 N 3Cl – 20 N o Z is the top number on periodic table Ions Charged atoms Caused by the removal or addition of electrons Atoms gain electrons to form an anion (overall negative charge) Atoms lose electrons to form cations (overall positive charge) General Chemistry Lecture 6 9/25/16 Multi-electron Atoms vs. Hydrogen In a Hydrogen atom, all subshells of a principle shell (n) are all at the same energy level Ex: o In a Hydrogen atom, 3s orbital has the same energy as 3p and 3d orbitals o Orbital energies are lower in multi-electron atoms than in Hydrogen atoms In a multi-electron atom, the various subshells of a principle shell are at different energy levels, but all orbitals within a subshell are at the same energy level Ex: o 3s orbital is at a lower energy than the 3p orbitalx 3p has the same energy ay 3p In higher number principal shells of multi-electron atom, some subshells of a different principal subshell nearly identical energies In a particular principal n level: o S orb < P orb < D orb < F orb An s electron penetrates through inner shell electrons to approach nucleus, thus more probability of finding it near the nucleus o Experiences greater nuclear charge o At lower energy due to distance between charges o Zero probability of finding the electron near the nucleus, has a node through nucleus, less penetrating than an electron Electron Configurations Ways to represent: o SPDF notation: Uses a number to designate a principal shell and letter (spdf) to identify the subshell with a superscript number following to indicate the number of electrons in that orbital. Empty subshells are not included o Ex: Nitrogen (N): Z=7 (7 electrons) – spdf notation: 1s 2s 2p o Orbital Diagram: 1s 2s 2p Paired electrons must have opposite spin shown by opposing arrows o Noble Gas Core 2 2 6 2 5 Chlorine (Cl): Z=17 – spdf notation spdf notation: 1s 2s 2p 3s 3p Look for noble gas (group 8a) that precedes the element In this case, Neon (Ne) precedes chlorine so the noble gas core notation is: 2 5 [Ne]3s 3p Rules for Configuration 1. Electrons occupy orbitals of lowest energy levels possible first 2. Pauli’s E▯▯lusio▯ p▯i▯▯ipal: No 2 ele▯t▯o▯s i▯ sa▯e ato▯ ▯a▯ ha▯e all fou▯ ▯ua▯tum numbers alike. An atomic orbital can only accommodate 2 electrons, and therefore they must have opposite spins General Chemistry Lecture 6 9/25/16 3. In a group of orbitals of identical energy, electrons enter empty orbitals whenever possible to minimize repulsion. 4. Electrons in half filled shells must have parallel spins 5. The Aufbau Principal: Hypothetical process where we build up each atom from the one that precedes it in atomic number Ground State Electron Configuration Where higher energy orbs are filled before lower energy orbitals 2 1 1 If you saw spdf notation: 1s 2s 2p it ▯ea▯s the ato▯ is i▯ a▯ ▯e▯▯ited▯ state General Chemistry Lecture 7 9/25/16 Transition Elements These are B-group elements The subshell being filled in the Aufbau process is an inner principal shell With principal quantum number lower than outermost occupied Ex: o Scandium (Sc): Z=21 o Minimum number of orbitals needed is 11 (because 11*2=22) o 1s 2s 2p 3s 3p 4s 3d o 1 1 3 1 3 1 5 electron orbitals (2 electrons per orbital) 2 2 6 2 1 2 1 o SPDF: 1s 2s 2p 4s 3d = [Ar] 4s 3d Exceptions for Transition Elements Chromium (Cr): [Ar] 4s 3d (all half-filled shells) Copper (Cu): [Ar] 4s 3d0 (inner shell filled) Silver (Ag): [Ar] 5s 4d Gold (Au): [Xe] 4f 6s 5d10 Magnetic Properties Paired and unpaired electrons If all electrons in atoms, ions, or molecules of a substance are paired, the substance is weakly repelled by a magnetic field. This is diamagnetism Atoms, ions, or molecules having at least one unpaired electron are attracted by a magnetic field. This is paramagnetism To answer a question about paired and unpaired electrons or paramagnetism/diamagnetism, write electron configuration as an orbital diagram o Odd number electron always paramagnetic, otherwise must check o Example questions: Which one has 5 unpaired electrons? How many unpaired electrons does this atom have? Ex: o Silicon (Si): Z=14 o [Ne] 3s3p [Ne]=10 electrons 3s paired, 3p unpaired Using the Periodic Table to Write Electron Configurations When you find the atom you are asked about: o S-block: Fill in ns shell o P-block: Fill in np shell o D-block: Fill in (n-1)d shell o F-block: Fill in (n-2)f shell General Chemistry Lecture 7 9/25/16 Valence Shell Outermost occupied shell For main group elements, group number is equal to valence number i.e. group 1A has one valence electron 1 Electron configuration that ends with ns correlates with period number Core electrons – electrons in inner shell, principle quantum numbers less than n Ex: 2 2 o Calcium (Ca): [Ar]4s where 4s are valence electrons **Know classifications in periodic table Ex: o Group 1A: Alkali metals o Group 7A: Halogens Periodic Properties of Elements Atomic radius o Covalent radius of an atom ½ the distance between nuclei of 2 identical atoms joined in a molecule (for nonmetals) o For metals: ½ the distance between nuclei of adjacent atoms o Trend: Atomic radii increase from top to bottom within a group on periodic table. This is because as n increases, size increases o The electrons in valence shell are further away from the nucleus as n increases so electrons are not pulled as strongly (Coulomb’s Law) and so there are wider berths General Chemistry Lecture 7 9/25/16 o Trend: Atomic radii of the main group elements (group 1A to 8A) decrease from left to right across the periodic table. This is because effective nuclear charge increases across a period from left to right Atomic radius increases Periodic Table Atomic radius decreases Atomic radii for transition elements within a period stay about constant because electrons are added to inner shells and thus keep effective nuclear charge constant and valence electrons at same distance from the nucleus Ions Anions o Add additional electron to the valence shell of the neutral non-metal atom o Number of electrons added to the non-metal is usually to fill valence shell (to attain noble gas configuration) o Ex: Oxygen (O): Z=8, 2s 2p , to get to noble gas (Neon) Oxygen gains 2 electrons Cations o Remove electrons from valence shell until previous noble gas configuration is reached and appropriate cationic charge is reached **Always write electron configuration for the neutral atom first. Then add/subtract valence shell to get appropriate ionic configurations Ions for Main Group Elements 1A – +1 charge ion 2A – +2 charge ion 6A – -2 charge ion 7A – -1 charge ion th The electron configurations of cations of p-block metals of the 4 period and beyond do not correspond to that of a noble gas 2 10 2 o Tin (Sn): [Kr] 5s 4d 5p o Sn : [Kr] 5s 4d10 +4 10 o Sn : [Kr] 4d For cations formed from transition metal atoms, the removal must first occur in the valence shell, and then, if necessary, into the inner shell o Iron (Fe) [Ar] 4s 3d 3+ 5 o Fe : [Ar] 3d
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