Chem 110 Notes (Exam 2) PDF

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Exam 2 Study Guide Class Notes ● Ions → atoms with a charge ○ Caused by a different number of electrons ■ Extra electrons = (-) charge - anion ■ Fewer electrons = (+) charge - cation ○ Ex. Sodium (Na) ■ 11 -- Na -- 22.99 ● 11 is the # of protons ● If neutral, # of protons = # of electrons, Na = 11e^○ Ex. Na with -1 electron ■ Na with 11 protons } charge = +1 → Na^+ or Na^+1 ■ Na with 10e^} ○ Ex. How many electrons (e^-) in O^-2 ← 2 extra electrons ■ Atomic # = protons = 8 ■ Neutral O = 6e^● 8e^- + 2e^- = 10e^○ Electron configuration → electrons exist in “shells” ■ For shell n, it holds 2n^2 electrons ● Shell #1 (n=1), hold 2(1)^2 = 2e^● Shell #2 (n=2), hold 2(2)^2 = 8e^● Shell #3 (n=3), hold 2(3)^2 = 18e^■ The higher the shell, the higher the energy (or reactivity) ■ Atoms always fill electrons from lowest to highest energy ■ → highest shell that has electrons is called the “valence shell” (valence electrons) ○ Ex. Boron 5e^-

○ Ex. How many valence electrons (e^-) are in Na? ■ Na = 11e^-

○ Can get valence e^- from the periodic table

Lewis Structures ○ Show valence e^- as dots

○ Ex.

(2 extra electrons for Oxygen)

○ Ex. Show the Lewis Structure for Na+

■ ○ Draw the Lewis Structure for N^-1

○ Octet Rule → main group elements like to have 8 valence e^○ Exceptions: H & He like just 2 valence electrons ○ Group I + II like empty shells (0 valence) ○ Ex. Fluorine

○ ○ Ex. Oxygen

○ Ex. Mg

● Ionic Compounds ○ A compound composed of anion(s) and cation(s) ■ Total charge = 0 ○ Ex. Na+ and Cl■ NaCl ○ Ex. Ca+2 and F■ CaF2 ○ Ex. Mg+2 and O^-2 ■ MgO

● Transition Metals ○ Can have multiple different values (always +)  ○ Ex. Cu+2  and Cl- ■ Answer: CuCl2 ○ Ex. CuBr → What is the charge on the atoms  ■ Cu+1  and Br- ○ Ex. Fe2O3 ■ Fe+3 and O-2 ● Naming Ionic Compounds (cation)(anion) + “ide” ○ NaCl = Sodium Chloride ○ Na2O = Sodium Oxide ○ AlCl3 =  Aluminum Chloride ○ Li3N = Lithium Nitride ● Naming Ionic Compounds with Transition Metals ○ Charge of the metal is written as a roman numeral ○ Ex. CuCl2 ■ Copper (II) Chloride ○ Ex. Fe2O3 ■ Iron (III) oxide

● Polyatomic Ions - a group of atoms that make an ion

● Ex. Iron (III) Sulfate ○ Fe+3 and SO4-2 ■ Fe2(SO4)3 ○ Sodium Phosphate ■ Na+ and PO4-3 ■ Na3PO4

● Ionic Compounds: anions + cations ○ Metal + nonmetal ■ NaCl ■ FeSO4 ● → held together by the attraction of (+)(-) ○ = Ionic Bond

○ Covalent Compounds ■ Non-metals share electrons in a covalent bond ■ Atoms are neutral (no (+) or (-)) = Ionic Bond ■ Atoms bonded to themselves are also covalent (H2) ● → Compounds in covalent bonds share electrons in order to get 8e^- in their valence shell (Octet rule) ● Exceptions: H & He ● Group I & II ■ Ex. H2 N  2 O  2 NF  3 CO  2 PCl  3 P  2O5 ■ Note: the element lowest / to the left of the periodic table is written first ○ Naming Covalent Compounds ■ Prefixes: mono = 1 , di = 2, tri = 3, tetra = 4, penta = 5, hexa = 6 ○ For AxBy ■ Name = (Prefix x)(Atom A) (Prefix y)(atom B) ■ Ignore “mono” for first atom ○ Ex. CO2 =  carbon dioxide ■ P2O5 =  Diphosphorus pentoxide ■ PCl3 =  Phosphorus trichloride ■ SO = Sulfur monoxide ○ Types of Covalent Compounds ■ Atoms usually share 1, 2, or 3 electrons ● Making single, double, or triple bonds ■ Some atoms keep pairs of electrons to themselves ● Called “non-bonding” or “lone pairs” ● Lewis Structures of Covalent Compounds ○ Lone pairs shown as 2 dots ○ Shared electrons are shown as a line ■ Single line = 1 pair of electrons → single bond ■ Double line = 2 pairs of electrons → double bond ■ Triple line = 3 pairs of electrons → triple bond ● Ex. Methane CH4 ○ 4 single bonds ○ Each bond = 2 electrons and 8 valence electrons in Carbon

● NH3 ○ Nitrogen has 8 valence electrons

● Molecular Shape Summary ○ No L.P.’s → same as electron geometry ○ 4 bond areas → tetrahedral ○ 3 bond areas + L.P → trigonal pyramidal ○ 2 bond areas + L.P.(s) → Bent ■ Note: charges (+)/(-) don’t change anything

● Physical Change - change in physical property ○ Melting, boiling, subliming ○ No change in the identity ■ Ex. snow → water ● H2O(s) and H2O(l)  ● Chemical Change - molecules react to make a new compound ○ A+B-C→A-B+C ■ Atoms are not destroyed ■ New bonds are formed ○ Signs that a chemical reaction has happened ■ Gas is produced (bubbles) ■ Solid is produced (precipitation) ■ Color change ■ Temperature change ○ Writing chemical reactions ■ Reactants (starting material) → Product ○ Ex. MgO + C → CO + Mg ■ Magnesium Oxide + Carbon → Carbon Monoxide + Magnesium ● Conservation of Mass - Atoms are not created nor destroyed

Sapling A. Ions & Lewis Structures for Atoms   a. The Fe2+  and the Fe3+  ions have the same number of protons +  b. The K ion is formed when a potassium atom loses one electron c. Overall charge = protons - electrons

d.

B. Ionic Formulas & Names a. Potassium Oxide i. K2O because Oxygen has a -2 charge

ii.

A. Polyatomic Ions B. Naming Covalent Compounds C. Lewis Structures and the Shape of Molecules v2

D. Physical and Chemical properties a. Chemical Changes (susceptibility to rust, flammability) i. Two clear colorless salt solutions are mixed and a bright orange precipitate forms ii. A silver teapot turns black iii. A candle is burned iv. Gasoline is burned v. Copper roof turns green over time vi. Baking soda is dissolved in vinegar and bubbles  form b. Physical changes (melting point, boiling, conductivity) i. Water is frozen ii. Water is heated up iii. Water is boiled iv. Gasoline is evaporated v. Candle wax is melted

vi. vii. viii. ix.

Sugar crystals are ground to a fire powder Sugar is dissolved in water A warm soda bottle fizzes when opened A fog appears on the windshield in cold weather

E. Chemical Reactions and Balancing v2

● Calcium has a +2 charge and Chlorine/Hydroxide have a -1 charge

HW Assign from book a. Reading 4.2-4.4 (Problems: Ch.4: 27-29, 35, 39-44) b. 27. Name the following covalent compounds i. BF3 - Boron trifluoride ii. SF4 - Sulfur tetrafluoride iii. ClF3 - Chlorine trifluoride iv. OF2 - Oxygen difluoride c. 28. Name the following covalent compounds i. NF3 - Nitrogen trifluoride ii. SCl2 - Sulfur dichloride iii. CF4 - Carbon tetrafluoride iv. CS2 - Carbon disulfide d. 29. Write the proper formula for the following covalent compounds i. Disulfur dichloride - S2Cl2 ii. Dinitrogen pentasulfide - N2S5 iii. Sulfur tetrafluoride - SF4 iv. Sulfur trioxide - SO3 e. 35. What is the formula and charge for each of the following polyatomic ions? i. Nitrate ion - NO3ii. Hydroxide ion - OH- iii. Cyanide ion - CN- iv. Phosphate ion - PO4 3f. 43. Name the following compounds i. CuCl2 - Copper (II) Chloride ii. Co(NO3)2 - Cobalt (II) nitrate

iii. iv.

CuCl - Copper (I) Chloride CrO - Chromium (II) Oxide

Be careful when naming ionic compounds (ignore numbers) vs. covalent compounds g. Reading 5.1, 5.5 i. Problems: Ch.5: 27, 28, 35 (a,c,d), 36 (a), 39, (a, c, d), 40 (a) h. 27. Draw the Lewis structure showing the bonding between the nitrogen and iodine

atoms in NI3 i. 6 lone pairs on each iodine and then each single bonded to Nitrogen which has 2 lone pairs i. 28. Draw the Lewis Structure showing the bonding between the two Bromine atoms in Br2 i. 6 lone pairs on each Bromine and Br is attached to Br with a single bond j. 35. Determine the electron geometry for the following compounds from Problem 31 i. a) PF3 - tetrahedron ii. c) CCl4 - tetrahedron iii. d) AsH3 - tetrahedron k. 36. Determine the electron geometry for the following compounds from Problem 32 i. a) H2S - tetrahedron l. 39. Determine the molecular geometry for the following compounds from Problem 31 i. a) PF3 - trigonal pyramidal ii. c) CCl4 - tetrahedral iii. d) AsH3 - trigonal pyramidal m. 40. Determine the molecular geometry for the following compounds from Problem 32 i. a) a) H2S - bent

n. Reading 8.1-8.8 Physical changes do not alter the chemical identity of a substance, whereas chemical changes result in the formation of a new substance 15. Identify each of the following as either a chemical change or physical change? ○ Evaporation of gasoline - physical change ○ Toasting a marshmallow - chemical ○ Filtering a pond water sample - physical ○ Burning documents - chemical 16. Identify each of the following as either a chemical change or physical change? ○ Formation of clouds and rain - physical ○ Freezing biological samples for storage - physical

○ Baking bread dough - physical change ○ Detonation of TNT - chemical change 17. Identify each of the following as either a chemical change or physical change? ○ Hardness - physical ○ Corrosiveness - chemical ○ Flammability - chemical ○ Color - physical

Labs ● Hydrogen has 1 single bond with a total of 2 electrons ● Oxygen has 2 single bonds or 1 double bond with 2 lone pairs for a total of 8 electrons ● Nitrogen has 3 single bonds, 1 triple bond, or a single and a double bond for a total of 8 electrons ● Carbon has a total of 8 electrons ● Hard water is water that contains magnesium, salts of calcium, and iron among other dissolved minerals...