CHEMISTRY REVIEW The following is a BRIEF overview of some important topics from General Chemistry I (CHEM 161) at HCC. In CHEM 161 here, we cover Chapters 1 – 12. General Chemistry II (CHEM 162) assumes that you have a mastery of this material. 1/14/2019

CHEMISTRY REVIEW Significant figures – you are expected to use them in calculations. Most answers typically rounded to two or three places. In lab work, it is often critical that you round answers properly. 1/14/2019

CHEMISTRY REVIEW Dimensional Analysis – a system using units along with numbers. When used properly in calculations, all units cancel except desired units. Example – convert 2.5 pints to Liters 2 pt = 1 qt, 1 qt = 946 mL, 1 L = 1000mL 1/14/2019

CHEMISTRY REVIEW Density problems D = m / V Ex) A concrete block has dimensions of 12.0” x 12.0” x 4.0”. If the density of concrete is 3.0 g/cm3, then what is the mass of the block? 1/14/2019

CHEMISTRY REVIEW Periodic Table Groups Periods Main Group elements and Transition Group elements Metals and Non-metals Periodic Trends for radii, ionization energy, and electron affinity Electron Configurations 1/14/2019

CHEMISTRY REVIEW Nomenclature of Inorganic compounds depends on type of compound – Molecular or Ionic Molecular = two non-metals or metalloid with non-metal. Ionic = metal with a non-metal, but metal may have a fixed or variable charge. 1/14/2019

CHEMISTRY REVIEW Naming Molecular Compounds Name first element in formula first followed by second element name, but change to –ide. Then, use prefix to indicate how many of each (subscript #). Ex) CO2 = carbon dioxide Ex) PCl3 = phosphorus trichloride Ex) N2O5 = dinitrogen pentoxide 1/14/2019

CHEMISTRY REVIEW Naming Ionic Compounds Name metal first followed by name of non-metal, but change to –ide. If metal has a fixed charge, then no further action is needed. If metal has a variable charge, then put charge after metal in Roman Numerals. Ex) NaBr = sodium bromide Ex) FeCl3 = iron(III) chloride 1/14/2019

CHEMISTRY REVIEW Polyatomic Ions – a group of elements bound together with a net charge. These NEVER change names when using in nomenclature. Ex) Na2SO4 = sodium sulfate Ex) Ni(NO3)2 = nickel(II) nitrate 1/14/2019

CHEMISTRY REVIEW Ionic Formulas Need to remember how these are written – subscripts balance charge. Need to be able to split apart into correct number of ions. Ex) CaCl2 = Ca+2 + 2 Cl-1 Ex) Na2SO4 = 2 Na+1 + SO4-2 1/14/2019

CHEMISTRY REVIEW Balancing chemical equations – by inspection. Ex) __H3PO3  __PH3 + __H3PO4 Ex) __C3H8 + __O2  __CO2 + __H2O 1/14/2019

CHEMISTRY REVIEW Basic Stoichiometry 1 mole of anything = Formula or Molecular Weight Ex) 1 mole of Na2SO4 = 2(23.0g) + 1(32.1g) + 4(16.0g) = 142.1g 1 mole of anything = 6.02 x 1023 atoms or molecules or formula units Ex) 1 mole of CH4 = 6.02 x 1023 molecules of CH4 = 4 x (6.02 x 1023 atoms of H) 1/14/2019

CHEMISTRY REVIEW Coefficients in balanced chemical equations represent mole amounts. Ex) N2 + 3 H2  2 NH3 1 mol of N2 plus 3 mol H2 yields 2 mol NH3 Allows for the conversion of mass of one into mass of another. Ex) 2.50g of N2 = ?g of NH3 1/14/2019

CHEMISTRY REVIEW Solutions – concentration measured in Molarity (M) Molarity = Moles of solute / Liters of Solution Dilution problems – will use this a lot! M1V1 = M2V2 5.0 mL of 0.10M NaOH and 15.0 mL of water are added together. What is the new molarity of the NaOH? 1/14/2019

CHEMISTRY REVIEW Titration problems – allow us to calculate a specific quantity of an unknown solution. Very first lab will involve titration – and many others will use as part of the lab. Ex) What mass of Na2CO3 is present in 100.0mL of a solution if it required 28.5mL of a 0.105M HCl solution to reach the endpoint? The balanced reaction is: Na2CO3 + 2 HCl  H2O + CO2 + 2 NaCl 1/14/2019

CHEMISTRY REVIEW Acids – produce H+ in solution. Formula usually starts with an “H” Strong acids – completely ionize in water HCl, HBr, HI, HNO3, H2SO4, and HClO4 Weak Acids – partially ionize in water HF, HC2H3O2, etc. 1/14/2019

CHEMISTRY REVIEW Bases – produce OH- in solution Strong bases – completely ionize in water Group 1A and 2A hydroxides – NaOH, KOH, etc. Weak bases – partially ionize in water Nitrogen containing compounds – NH3, CH3NH2, etc. 1/14/2019

CHEMISTRY REVIEW Electron Configurations of the Elements Four types of orbitals – s, p, d, and f s = 1 orbital, p = 3 orbitals, d = 5 orbitals, and f = 7 orbitals Shorthand configuration of C: [He] 2s2 2p2 S: [Ne] 3s2 3p4 Fe: [Ar] 4s2 3d6 Number of unpaired electrons for atoms can be found using an orbital diagram. For ions, gain/lose electrons according to charge – for transition metals, lose s electrons first. 1/14/2019

Math Stuff Many equations involve the use of either the natural log or log functions. ln x or log x 1/14/2019

Math Stuff Some problems in chapter 14 will require use of the quadratic equation. Need to rearrange into: ax2 + bx + c = 0 1/14/2019

Math Stuff Example problem 16 = (2x)2 / [(0.5-x)(0.1-x)] 1/14/2019