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Covalent Compounds: Formation, Names, and Calculations

Learn about ionic and covalent compounds, how they form, naming conventions, formulas, percent composition, molar mass, and conversion between moles and particles. Identify, explain, and calculate various properties.

andrewmccoy
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Covalent Compounds: Formation, Names, and Calculations

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  1. Covalent Compounds

  2. Analyze ionic and covalent compounds in terms of their formation (electron sharing or electron transferring), names, and chemical formulas, percent composition, and molar mass. Today you will: • Identify covalent compounds • Explain how covalent compounds form • Name covalent compounds • Write formulas for covalent compounds • Calculate molar mass of a covalent compound • Calculate percent composition of a covalent compounds • Convert between moles, mass in grams, and number of particles (molecules) for a covalent compound

  3. Ionic vs Covalent – how do we tell the difference? • If it contains a metal, it is IONIC. • If it contains a cation and an anion, it is IONIC. • If electrons are transferred, it is IONIC. • If it contains two anions, it is covalent. • If electrons are shared, it is covalent. • If there are prefixes in the name, it is covalent.

  4. Covalent Bonds • Electrons are shared between 2 atoms. • When 2 or more atoms bond covalently, a molecule is formed. • Covalent bonds generally occur between elements that are relatively close to each other on the periodic table • Both element want to GAIN ELECTRONS • Both elements have HIGH ELECTRONEGATIVITY • Most are between non-metals

  5. Prefixes • Are used when naming covalent compounds. • Prefixes indicate how many atoms of each element are contained in the molecule. • Mono • Di • Tri • Tetra • Penta • Hexa • Hepta • Octa • Nona • Deca

  6. Naming Covalent Compounds • Name the first element in the formula, using its name • Name the second element, using the root of its name and adding “-ide” • Use PREFIXES to give the number of each atom present. • Do not usemono-on the first element

  7. Examples - Name the following covalent compounds: • NCl3 nitrogen trichloride • PF5 phosphorous pentafluoride • N2O7 dinitrogen heptoxide • CO carbon monoxide • CO2 carbon dioxide • CCl4 carbon tetrachloride • N2S4 dinitrogen tetrasulfide • NO nitrogen monoxide

  8. Write the formulas for the following covalent compounds • carbon tetrabromide CBr4 • dinitrogen monoxide N2O • arsenic pentaiodide AsI5 • sulfur hexafluoride SF6 • nitrogen triiodide NI3 • nitrogen monoxide NO

  9. Diatomic Elements • Elements that naturally exist as pairs in gaseous state. • As pairs, they are stable. • N2 (g) O2 (g) F2 (g) Cl2 (g) Br2 (g) I2 (g) H2 (g) • Helpful Hints to remember the diatomic elements: • There are 7 diatomics & the form the shape of a 7 on the periodic table (don’t forget hydrogen) • All elements ending with "-gen" including halogens • Bromine & Iodine are not diatomic at room temperature

  10. Diatomic Molecules

  11. Molar Mass • Also called the Formula Mass • in units of grams/mole (g/mol) • To find the molar mass of a compound, add up the mass of each element within the compound. • Example: water H2O • 2(1.008g/mol) + 1(15.999g/mol) = 18.015 g/mol

  12. Examples – Molar Mass Find the molar mass of the following compounds • CO2 Carbon Dioxide • 1(12.011 g/mol) + 2(15.999 g/mol) = 44.009 g/mol • CO Carbon Monoxide • 1(12.011 g/mol) + 1(15.999 g/mol) = 28.010 g/mol • Nitrogen triiodide NI3 • 1(14.007 g/mol) + 3(126.905 g/mol) = 394.722 g/mol • Diphosphorus PentoxideP2O5 • 2(30.974 g/mol) + 5(15.999 g/mol) = 141.943 g/mol

  13. Percent Composition • compares the mass of one part of the compound to the mass of the whole compound • In words - mass of element divided by the molar mass of the compound times 100 Mass of the Element x 100 Molar Mass of the Compound

  14. Example 1 – Percent Composition Find the percent composition by mass of oxygen in carbon monoxide. • Molar Mass = 28.010 g/mol • % Mass of Oxygen = 1(15.999) = 15.999 g/mol % Oxygen =

  15. Example 2 – Percent Composition Determine the approximate percent by mass of sulfur in dinitrogen pentasulfide. • Molar Mass = 188.339 g/mol • Mass of Sulfur = 5(32.065) = 160.325 g/mol % Sulfur =

  16. The MOLE • Grams Moles • Use Molar Mass (in units of g/mol) • Moles Number of Particles • Use Avogadro’s Number • 1 mole = 6.02x1023 particles • If the particles is: • an Element use ATOMS • an Ionic Compound use FORMULA UNITS • a Covalent Compound use MOLECULES

  17. Examples 1 & 2 – The MOLE • Find the mass of 7.50 moles of dinitrogen trioxide. 7.50 moles 76.011 g = 570. g N2O3 1 mole • Find the number of moles in a 135.0 g sample of sulfur hexafluoride. 135.0 g 1 mole = 0.9243 mol SF6 146.053 g

  18. Examples 3 & 4 – The MOLE • Determine the number of molecules in 12.5 moles of nitrogen monoxide. 12.5 mol 6.02x1023 molec. = 7.53x1024 molec. NO 1 mol • How many moles are contained in 1.25x1024 molecules of dinitrogen tetroxide. 1.25x1024 molec. 1 mol = 2.08 mol N2O4 6.02x1023 molec.

  19. Examples 5 & 6 – The MOLE • What is the mass in grams of 2.54x1026 molecules of dinitrogen monoxide? 2.54x1026 molec. N2O 1 mol 44.013 g N2O 6.02x1023 molec. 1 mol = 18600 g N2O • Determine the number of molecules in 65.8 grams of tetraphosphorus decaoxide. 65.8 g P4O10 1 mol 6.02x1023 molec. 283.886 g P4O10 1 mol = 1.40x1023 molec. P4O10

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