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ACS Review

ACS Review. Quick refresher of materials Some sample questions and short cuts. Sections in ACS prep book to review. Atomic Structure Molecular Structure and bonding Stoichiometry States of Matter/ Solutions Energetics Descriptive Chemistry/ Periodicity Laboratory Chemistry. Basics.

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ACS Review

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  1. ACS Review • Quick refresher of materials • Some sample questions and short cuts

  2. Sections in ACS prep book to review • Atomic Structure • Molecular Structure and bonding • Stoichiometry • States of Matter/ Solutions • Energetics • Descriptive Chemistry/ Periodicity • Laboratory Chemistry

  3. Basics • Dimensional analysis is very very important • Know how to make conversions • cent, kilo, ect. • Grams  moles (MM) • Vol  grams (density) • Vol  moles (concentration)

  4. The periodic table

  5. Notation and Calculation Remember this? 26 protons 30 neutrons 26 electrons Calculations: you may need to do weighted averages. 20% of a sample is 32grams/mol and 80% 28grams/mol what is the average? 20x32 + 80x28 /100 = 28.8g/mol

  6. The table • Which has the highest electronegativity? • Which is isoelectric to X? • Which is likely to form the same structure as __ ? • What has 25 protons? • If it has 24 neutrons and a mass of 52 what is the element?

  7. formulas Know how to use charges to determine formula Example: the correct formula for the compound formed between Al and S? Al+3 and S-2 Al2S3 Even more useful, use formula to determine charge. Example: you can’t remember if Ag has a +1 or +2 charge. if AgCl is a formula given in the question or in some other question, knowing Cl is -1 tells you Ag is +1

  8. Formulas from % • Given mass % or total mass of each element determine empirical formula. A sample contains 11.1% H and 88.9% O 11.2grams H (1 mol/1.001g)=moles H 88.9grams O(1 mol/16.0g)=moles O =11.18 2 1 H2O =5.55

  9. Single Double Composition Decomposition Combustion Acid / Base Balance equations know difference in General Ionic Net ionic stoichiometry Reactions

  10. Bronsted/ lowry Lewis Arrhenius Protons electron pairs What’s produced in water Acid base theories You should have your six strong acids and bases memorized. HCl, HBr, HI, HNO3, H2SO4, HClO4 LiOH, NaOH, KOH, CaOH2, SrOH2, BaOH2 • Why? • It helps identify weak acids and weak bases • It will help with determining solubility

  11. Yields • Balance equations • Use stoichiometry • Limiting reagents • Grams------mole------mole------gram • Amt------mole------mole-----amt • Amt -------- Mole • Grams (molar mass) • Liters of solution (concentration) • Gas (Ideal gas law)

  12. Solution • Molarity(M) Vs Molality(m) Total solution solvent and solute Solvent only Dilution: C1V1=C2V2 Titration: naMaVa=nbMbVb

  13. Gas laws • PV=nRT • Mostly the relationships (when P goes from 10-20, V does what?) • Remember T is in K • When gases are non ideal (correct for molecular volume and intermolecular forces) • Diffusion small things faster

  14. Structure • Quantum numbers • n is the major shell(1,2,3… • l is the subshell (0=s, 1=p) • ml is the axis (x, y, z) • s spin (+ ½ ) • Filling the orbital (use the table)

  15. Bonding and geometry • Ionic vs. Covalent • Electronic vs. Molecular geometry (VSEPR) • Drawing Lewis structures • Dipoles • Hybrids • Pi bonds • MO • Delocalized bonds (resonance)

  16. -1 -3 +1 Lewis structures • Multiple Choice Test Just be able to pick the correct drawing!! • Some things to look for • Octets on non-central atoms (all atoms if central is 1st row) • Happy elements • Charges • Negative usually carried by single bonded O (one for each charge) • Positive usually carried by a four bond N or P

  17. Freezing / melting Liquid Solid Condensing / boiling Gas Sublimation / Deposition Triple point States of matter Know the basic properties Remember this:

  18. Solid at STP Diatomic gas at STP energy • Heat of formation ( to form from the elements) • DHf of MgCl2 is Mg(s) + ½ Cl2(g) MgCl2DH=___kJ • Heat of combustion(react with O2) • DH of CH4 is CH4 + 2O2(g) CO2 + 2H2O DH=___kJ State function have D which means final - initial

  19. Energy Bond Enthalpy = Sum of bond energy of reactants - sum of bond energy of products (Breaking bonds- forming bonds) Enthalpy of reaction using DHf= sum of products – sum of reactants Hess’s Law===Get to the goal by manipulating reaction information given and adding up the reactions used

  20. When Solving Problems • Look for the easiest way to solve! There are 70 questions and only 110 minutes so THERE MUST BE SHORT CUTS!

  21. Which of these compounds contains the greatest percentage of nitrogen?A) C6H3N307B)   CH4N20C)   LiNH2D)   Pb(N3)2 C6H3N307229 g/mol CH4N20 60.1 g/mol LiNH223.0 g/mol Pb(N3)2 229.1 g/mol The long way: calculate the %N for each one The quicker way: all N have the same mass so, Which has the highest N to mass ratio or Even better which has the lowest total mass per N A cursory glance tells us it is not B or A D has 6 N it may need a second look 229/6=38 The answer is C

  22. The Number of atoms in 9.0g of Aluminum is equal to the Number of atoms in A)   8.1g MgB)   12.1g MgC)   9.0g MgD) 18.0g Mg The Long way: Calculate # of atoms in 9.0 g Al Then calculate mass of that # of Mg atoms Look for ratios: Al has a molar mass of 27 This is 1/3 of a mole Al Which one is 1/3 mole of Mg 24.3 x 1/3 = 8.1g So “A”

  23. When NF3 and BF3 are reacted together they form BF3NF3 what is the geometry of the B and N atoms.A) Both tetrahedralB) B is triganal planer and N is tetrahedralC) Both triganal planerD) N is triganal planer and B is tetrahedral How many things are around each? B and N each will have 4 bonds Both tetrahedral

  24. Mol/L of solution ¼ L of 0.1M A student wants to prepare a 250mL sample of 0.10 M NaCl. Which procedure is the most appropriate? Molar mass of NaCl 58.4 g·mol-1A)    Add 5.84g NaCl to 250mL of waterB)    Add 1.46g of NaCl to 250mL of waterC)    Dissolve 5.84g of NaCl in 50mL and Dilute to 250mLD)    Dissolve 1.46g of NaCl in 50mL and Dilute to 250mL So A and B are out 5.84 is 0.1 mole NaCl So “D” 1.46 is ¼ of that

  25. The oxidation number of chlorine in KClO3 isa) +6b) +5c) -1d) -2e) +2 O only oxidation is –2 (unless peroxide) 3 x -2 = -6 K only oxidation +1 1 x +1 =+1 -5 +5 to Balance it out B

  26. Which one of the following sets of quantum numbers is not allowed?a) n = 3, l = 2, ml = +1b) n = 3, l = 3, ml = 0c) n = 3, l = 0, ml = 0d) n = 4, l = 3, ml = -2 l must be less than n ml absolute value must be less than or equal to l B

  27. Cr+2 • Fe+2 • Ni+2 • Cu+2 Which ion has 26 electrons? Its really asking “Which is iso-electronic to Fe?” On the table “What minus 2 electrons looks like iron?” C  Ni+2

  28. Element X has two isotopes 13X with 80% abundance and 12X with 20% abundance, what is the average mass of the element? a) 12. amub) 12.8 amuc) 12.5 amu d) 13.0 amu Long way: (13 X 80) + (12 X 20)/100 But why bother: the weighted average will be closer to the larger abundance B

  29. GOOD LUCK!!! • 10 AM class your final is Friday April 27 at 8 am in LCTR 346 • 11 AM class your final is Monday April 30 at 8 am in LCTR 346 • You must get permission to switch from one time to another.

  30. SI sessions and Office Hours • SI sessions in RHSC 317 Tuesday at 5 pm and Wednesday 8 pm • Offices Hours— • Wednesday (April 25th)11-4 • Thursday (April 26th) 11-4 • Sunday (April 29th)12-3

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