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CHE 117A

CHE 117A. Review and Refresh. Review and Refresh. Every Substance is composed of atoms An atom is the smallest possible particle of a substance Atoms are extremely small. Review and Refresh. In most substances atoms combine to form molecules

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CHE 117A

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  1. CHE 117A Review and Refresh

  2. Review and Refresh • Every Substance is composed of atoms • An atom is the smallest possible particle of a substance • Atoms are extremely small

  3. Review and Refresh • In most substances atoms combine to form molecules • A molecule is a combination of two or more atoms held together in a specific shape by attractive forces

  4. Review and Refresh • A substance that contains only one type of atom is called and element. • O • Oxygen • Na • Sodium • Br • Bromine • Sn • Tin

  5. Review and Refresh • Elements combine to form compounds • The relative amounts of the elements in a compound never change • This ratio is shown in the chemical formula of the compound • O2, H2O, CO, CH4

  6. Review and Refresh

  7. Review and Refresh • The elements can be grouped according to their physical and chemical properties • Periodic table • Metals on the left • Nonmetals on the right

  8. Review and Refresh

  9. Review and Refresh • Elements combine to form compounds which can exist in three different phases • Solid, liquid, and gas

  10. Review and Refresh • Changes between phases are physical changes • The substance’s chemical nature remains the same • Ice melting to water • Water converting to steam • Sugar dissolving in water • Chemical changes involve one substance becoming another substance • C burning in O2 to form CO2

  11. Review and Refresh • Scientific Notation • 650,000,000 is 6.5108 • 0.0000000100 is 1.0010-8

  12. Review and Refresh • Units • G = giga = 109 • M = mega = 106 • k = kilo = 103 • c = centi = 10-2 • m = milli = 10-3 • µ = micro = 10-6 • n = nano = 10-9 • p = pico = 10-12

  13. Review and Refresh • Unit conversions • Example 1: The speed of light is generally accepted to be 3.00108 m/s. What is the speed of light in mph? • 1 mile = 5280 ft • 2.54 cm = 1 in

  14. Review and Refresh • Three temperature scales • °F, °C, K • °F = 1.8°C + 32 • K = °C + 273.15

  15. Review and Refresh • Precision describes the exactness of a measurement • Accuracy describes how close a measurement is to the true value

  16. Review and Refresh • Example 2: Significant Figures

  17. Review and Refresh • Back to molecules… • The chemical formula describes the composition of a substance • for most elements, the formula is the chemical symbol • seven diatomic elements: H2, N2, O2, F2, Cl2, Br2, I2 • also, P4 and S8

  18. Review and Refresh • When to different elements combine to form a binary compound, the chemical formulas are written as follows • Usually the element farther to the left on the periodic table is written first • KCl, Al2O3, Mg3N2

  19. Review and Refresh • H is only written first when combined with elements from Groups 6 and 7 • H2O, HCl • NaH, B2H6, CH4 • If the elements are in the same group, the lower element is written first • SeO2, IF3

  20. Review and Refresh • Example 3: • Write the correct chemical formulas for the following sulfur compounds

  21. Review and Refresh SO3 H2S SF4 S2F2

  22. Review and Refresh • Chemical formulas only give the ratio of elements in a compound • they say nothing about the arrangement of the elements relative to each other • Structural formulas give both • Propane, C3H8

  23. Review and Refresh • Often two very different compounds have the same chemical formula • C2H6O

  24. Review and Refresh • We can also represent structural formula in 3D • ball-and-stick model • space-filling model

  25. Review and Refresh

  26. Review and Refresh • We can simplify line structures even further • C-H bonds are not drawn • C is not labeled • C always has 4 bonds

  27. Review and Refresh

  28. Review and Refresh

  29. Review and Refresh

  30. Review and Refresh • Example 4: • Write the chemical formula for the following compounds C2H4Cl2 C4H8O2 C3H4O

  31. Review and Refresh • Naming Compounds: binary compounds • Elements that appear first keep their name • Second element is named with the root name plus –ide • Use greek prefixes to represent number of atoms • never use mono- for the first element

  32. Review and Refresh • CO • carbon monoxide • NO2 • nitrogen dioxide • SO3 • sulfur trioxide • P4O10 • tetraphosphorus pentoxide

  33. Review and Refresh • Ionic compounds are named with the cation first and the anion second • Memorize Table 3.5 • NaCl • sodium chloride • NH4NO3 • ammonium nitrate

  34. Review and Refresh • If the compound has a transition metal then the charge of the metal is indicated in the name by a Roman numeral • FeCl3 • iron(III) chloride • Cu2O • copper(I) oxide

  35. Review and Refresh • The mole • a mole of any substance is equal to 6.0221023 (NA) items of that substance • exactly like a dozen eggs • Obviously we can’t count that many items • so we count mole by mass

  36. Review and Refresh • 12g of carbon-12 contains exactly one mole of atoms • all other molar mass are based on this value • the atomic mass on the periodic table is the mass in grams of one mole of the element

  37. Review and Refresh • The molar mass of a compound is simply the sum of the atomic masses of the constituent elements • Example 5: • What are the molar masses (molecular weights) of NaCl and C3H8 • 58.44 g/mol and 44.10 g/mol

  38. Review and Refresh • Example 6: • How many moles of NH4NO3 are contained in 16.5 g of the compound?

  39. Review and Refresh • Suggested Problems • Chapter 1 • 8, 10, 12, 26, 33, 34, 40, 41, 55, 61, 69, 87, 88, 98 • Chapter 3 • 2, 5, 8, 9, 10, 15, 16, 24, 31, 35, 38, 41 – 43, 72, 81, 95, 101, 108

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