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Formulas and Math

Formulas and Math. Binary Compounds. “Bi” means 2 Binary compounds are formed between 2, different elements Ex: H 2 O and NaCl. Rules:. 1) Write the positive element 1 st with it’s oxidation # on top ex – Magnesium Chloride – Mg +2

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Formulas and Math

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  1. Formulas and Math

  2. Binary Compounds • “Bi” means 2 • Binary compounds are formed between 2, different elements • Ex: H2O and NaCl

  3. Rules: 1) Write the positive element 1st with it’s oxidation # on top ex – Magnesium Chloride – Mg+2 2) Write the negative element next to it with it’s oxidation # on top ex – Mg+2Cl-1 3) Criss-cross the oxidation #s down and drop the signs ex – Mg+2Cl-1 Mg1Cl2 4) Reduce, drop ones, remove any GCFs ex – MgCl2

  4. Calcium Sulfide • Ca+2 • Ca+2S-2 • Ca+2S-2 • Ca2S2 • CaS

  5. Ternary Compounds • Ternary compounds are comprised of 3 different elements. • Ex: K2SO4 and KOH • Reference Table E

  6. Rules: 1) write the positively charged ion 1st, with its oxidation # on top • if it is a polyatomic ion then place the formula in parenthesis • Ex – potassium sulfate – K+1 2) write the negatively charged ion 2nd, with its oxidation # on top • if it is a polyatomic ion then place the formula in parenthesis • Ex – K+1(SO4)-2 3) criss-crossthe oxidation #s, placing the # outside of the parenthesis, and drop the sign • Ex – K+1(SO4)-2 4) reduce and rewrite • Ex – K2SO4

  7. Ammonium Fluoride • (NH4)+1 • (NH4)+1F-1 • (NH4)+1F-1 • (NH4)1F1 • NH4 F

  8. Chemical Nomenclature • Hydrogen with a nonmetal • Ex – H2S • 1. Name hydrogen 1st • 2. Name the 2nd element – change the ending to –ide • Hydrogen sulfide You try: H3P HBr H2Se Hydrogen phosphide Hydrogen bromide Hydrogen selenide

  9. Chemical Nomenclature • Metal having only one oxidation number with a nonmetal • Ex – AlBr3 • Name the metal first (aluminum) • Name the nonmetal with the –ide ending • Aluminum bromide • You try… • Na2S CaCl2 AlBr3 • Sodium sulfide Calcium chloride Aluminum bromide

  10. Easy Schmeesy

  11. Chemical Nomenclature • Metal with more than one possible oxidation # with a nonmetal • Ex – FeCl2 • Name the metal – iron • Uncriss-cross the subscripts to determine the oxidation # used - FeCl2 • Fe+2Cl-1 • Check the second element’s ox # to make sure you didn’t reduce • Write the roman numeral, in parenthesis, equal to the oxidation # used – (II) • Name the nonmetal with the –ide ending • Iron (II) chloride

  12. You Try… • HgCl2PbS TcF7 • Mercury (II) chloride Lead (II) sulfide Technetium (VII) fluoride

  13. Chemical Nomenclature • Two nonmetals together • Use the prefix that corresponds to the subscript for the first element and then write the name of that element • If the subscript is one, you do not have to use mono for the first element • Use a prefix that corresponds to the subscript for the second element and then write that name, with the –ide ending • Ex – CO = carbon monoxide • Ex – N2O4 = dinitrogentetraoxide

  14. You try… • O2F2 SiF4 P4O10 • Dioxygendifluoride silicon tetrafluoridetetraphophorusdecoxide

  15. Naming Recap • To decide which set of rules to follow to name a compound… • 1 – Decide what type of element the first element in the compound is • If it is a pure metal with only one oxidation # EASY SCMEESY - just name it, no numbers, no worries • If it is a metal with multiple oxidation #s ROMAN NUMERAL – uncriss-cross and determine the oxidation # used • If it is a nonmetal PREFIXES – no not uncriss-cross!!! Just write the prefix equal to the subscript of that atom

  16. Gram Formula Mass • The sum of the masses of all of the elements in a molecule

  17. Molecule • a neutral substance in which the atoms are bonded to each other only by covalent bonds. All noble gases are also considered molecules, even though there is not covalent bonding present, because they are neutral and stable.

  18. Mole • 6.02 x 1023 particles of anything • 1 mole of munchkins would cover the surface of the earth to a depth of 5 miles!!!

  19. GFM Example • C6H12O6 • Element Mass X Subscript = Total • Carbon 12.0 X 6 =72.0 • Hydrogen 1.0 X 12 =12.0 • Oxygen 16.0 X 6 =96.0 • = 180.0 g/mol

  20. Molar Conversions • Remember, 1 mole of any gas contains 6.02 x 1023 particles. • How many particles would be in ½ of a mole • (6.02 x 1023particles)/2 = 3.01 x 1023 • How many particles would be in 3 moles of a gas? • (6.02 x 1023particles) x 3 = 18.06 x 1023

  21. Mole Calculations See Table T given mass Number of moles = gram-formula mass • What is the mass of 2.94 moles of Au? • # moles = 2.94 • Given mass = X • GFM of Au (from periodic table) = 197.0 g/mol • So… 2.94 moles = X 197.0 g/mol Cross multiply X = 579 grams

  22. Percent Composition Calculate the percent composition (by mass to the tenth’s place) of the compound MgCl2. Mg – mass = 24.3g x 1 atom = 24.3 g/mol Cl – mass = 35.5g x 2 atoms = 71.0 g/mol Total mass of MgCl2 = 95.3 g/mol %comp of Mg = 24.3/95.3 x 100 = 25.5% %comp of Cl = 71.0/95.3 x 100 = 74.5% As a check, when you are finished, total percentages should add up to 100%

  23. Molecular Formula • Gives the actual # of atoms of each element in the compound • Example – glucose C6H12O6 • 6 carbon atoms • 12 Hydrogen atoms • 6 oxygen atoms

  24. Empirical Formula • Gives the simplest mole ratio among the elements in the compound • It is the molecular formula reduced to lowest terms

  25. Determining the Molecular Formula • You can determine the molecular formula of a compound if you are given the molecular mass and the empirical formula. • Find the mass of the EF. • Find the multiple that the formula was reduced by. • Multiply each subscript in the EF by this multiple.

  26. Example

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