Chem 1070 Week 2 Notes with Examples
Chem 1070 Week 2 Notes with Examples CHEM-1070-40
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This 6 page Class Notes was uploaded by Dkrefft on Friday September 4, 2015. The Class Notes belongs to CHEM-1070-40 at Tulane University taught by Lopreore, Courtney in Fall 2015. Since its upload, it has received 196 views. For similar materials see General Chemistry I in Chemistry at Tulane University.
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Date Created: 09/04/15
Chem 1070 8I319I4 Chapter 2 Continued Dalton s theory led to the law of multiple proportions if two elements from more than a simple compound the masses of one element combined with a fixed mass of a second element are in the ratio of small whole numbers 0 ie Carbon and oxide 0 1000g of carbon is combined with 1333g of oxygen CO 0 1000g of carbon is combined with 2667g of oxygen C02 0 the second sample has twice as much oxygen 0 26671333 2 0 Procedure fix one column to one gram by convention Change the second column the same way you changed the first column Show that column B is in whole number ratios 0 Subatomic particles all objects of matter made up of charged particles equal negative and positive amounts so it s neutral Opposites attract and like charges repel each other 0 Electrons Faraday made the first CRT cathode ray tube It passes electricity through a tube Cathode rays became electrons in 1874 Thompson concluded that electrons are fundamental particles of matter found in all atoms 0 Milliken determined the charge expressed in Coulomb s law Q 16022 x 1019 C 0 Mass of an electron 91094 x 1028g 0 Thompson predicted structure of atoms with plum pudding model Cloud of positive charges with electrons embedded in it 0 First hypothesis of alpha particles Nucleus Thanks to Rutherford and Geiger Used alpha particles as protons to study the inner structure of atoms gold foil experiment When the foil was bombarded o The majority of alpha particles were undeflected 0 Some were slightly deflected 0 Few were severely deflected 0 An even smaller number did not pass through but bounced back 0 A nuclear atom has three features 0 Most of the mass and positive ion charge are centered in a small region called the nucleus mostly just empty space 0 Magnitude of the positive charge is different for different atoms approximately half the atomic weight of the element 0 There are as many electrons outside the nucleus as there are unites of positive charges on the nucleus 0 Half of the nucleus is made up of two protons and the other half of two neutrons Electrons orbit the nucleus 0 The number of protons atomic number variable 2 0 Number of protons number of neutrons A atomic mass whole number integer 0 Atomic mass unit amu 112 of the mass of carbon12 grams per mol A C E Contrary to Dalton not all atoms of the same element have the same mass These are called isotopes lsotopes atoms that have the same atomic number but have a different mass number not whole numbers not all elements have this 0 Of all of the neon atoms on Earth 0 9051 are A 20 Z 10 o 027 are A 21 Z 10 o 922 are A 22 Z 10 0 Silver with a neutron value of 62 A 109 Z 47 0 Charge is the protons electrons in the upper right hand corner 0 Atomic mass naturally occurring carbon contains 13 C which is why atomic mass of carbon on the periodic table is 1201017 and not 12 Determined experimentally average of isotomic masses weighted with percent abundances 0 98931 carbon have a mass of exactly 12 the rest are 130 0 given the natural abundance Take the percent to scale the mass 0 Vertical column groups 0 Group one alkaline metals 0 Group two alkaline earth metals 0 Group seventeen halogens 0 Group eighteen noble gases 0 The elements are either metal right nonmetal left or metalloid on the staircase 0 Rows are called periods 0 Transition elements are groups 312 Mole SI unit that describes an amount of substance by relating it to the number of particles in that substance 0 Avogadro s number 6022x1023 0 M molar mass in gmol 0 Le Li 6941 gmol 0 What s the mass of 235x1024 atoms of Cu Know the mass of Cu 63546gmol Divide by Avogadro s number and set up proportion 63546g x 6022x1023 235x1024 X 248g Atomic mass is always in gmol Chapter 3 2 types of chemical bonds 0 covalent sharing of electrons between atoms Non metals 0 ionic more of an attraction than a bond Transferring electrons between two atoms 0 Molecular formula nonmetals Represented with formulas with relative number of atoms 0 lmperical formula simplest form Ratios Condensed structural formula written in a single line CH3COOH acetic acid tells a bit about the order of the atoms 0 Chemical formula C4H10 0 Organic compounds are compounds that contain hydrogens and carbons Carbon forms four covalent bonds Ionic compounds a metal and a nonmetal Metals tend to lose more electrons cation positive ie sodium Nonmetal gains electrons negativeanion ie chlorine We can deduce charge from what group the element belongs in Formula unit the smallest electrically neutral collection of ions ie NaCl Usually they re embedded and not distant NaCl is not a molecule but a formula unit Monoatomic ion made up of one atoms Polyatomic made up of two or more atoms p91 The can bond to a metal Molecule indicated covalent bonding Typically all nonmetals A formula unit has a formula mass Just add together the masses from the periodic table Molecular mass H20 21008 15999 180153 lonic compoundsMgCl2 Formula mass atomic mass Mg 2atomic mass of CI 24305 2354533 95211 Molar mass mass of one mole 6022E10A23 of compound 180153g H20 1mol Molar mass of H20 1 mole of H20 180153g H20 6022E10quot23 molecules of H20 Want to know the atoms Just multiply this by three How many nitrate atoms and how many oxygen atoms are present in 100 of MgN032 1 00 x 1 1molMgN032 6022E1023MgN032 39 10E106 14831g MgN032 1 mol MgN032 406E1015molecMgN032 2 No 3 812E1015No 3 ions 1 1MgN032 To find the oxygen atoms 406E1015molecMgN032 6 oxygen atoms 1 1 MgN032 244x10160xygen atoms How many atoms are in a piece of gold with density of 1932gcm3 250m diameter 250m width 0100mm high Get rid of the volume first Get everything in CM3 1m 100 cm 0100mm x x 00100cm 1000mm 1m 1932g 250cm250cm0010cm cm3 1208g Au density 9 volume 9 grams 9 mol 9 atoms 1mm 0006133 Au mol 1208 g Au x 196967g 6022E1023 369E1021 atoms Au mol 613E10 3m0l Au x
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