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Stoichiometry and Gases

Stoichiometry and Gases. By: Carson Ram & Thomas Schweinfurth. The Periodic Table. Atomic Number: Representative of the protons. Atomic Symbol: Letter representation of the element. Atomic Weight: Representative the neutrons & protons. Chalcogens. The Periodic Table. Halogens.

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Stoichiometry and Gases

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  1. Stoichiometry and Gases By: Carson Ram & Thomas Schweinfurth

  2. The Periodic Table Atomic Number:Representative of the protons Atomic Symbol:Letter representation of the element Atomic Weight:Representative the neutrons & protons

  3. Chalcogens The Periodic Table Halogens Family:Down acolumn 8A: Noble Gases 1A: Alkaline 2A: Alkaline Earth Metals Period:Across a row Metals Metalloids Nonmetals http://wps.prenhall.com/wps/media/objects/5524/5656731/ebook/blb11_flash_main.html?chapter=null&page=null&anchory=null&pstart=null&pend=nuall

  4. Atoms, Molecules, and Ions • Molecular Formulas: Indicate the actual numbers and types of atoms in a molecule • Empirical Formulas: Give only the relative number of atoms of each type in a molecule • Example… Molecular Formula C2H4 Empirical Formula CH2

  5. Chemical Nomenclature • Tips & Tricks for naming cations: • Cations formed from metal atoms have the same name as the metal: • Ex. Ca+2  calcium ion • If a metal can form different ions, the positive charge is indicated by a Roman numeral in parenthesis behind the name of the metal: • Ex. Fe2+  iron (II) ion Fe3+ iron (III) ion • Cations formed from nonmetal atoms have names that end in –ium: • NH4+ammon-iumion H3O+ hydron-iumion

  6. Chemical Nomenclature • Tips & Tricks for naming anions: (Part One) • The names of monatomic anions are formed by replacing the ending of the name of the element with –ide: • Ex. Br- Brom-ideIon Cl-Chlor-ide Ion • Polyatomic anions containing oxygen have names ending in –ate or –ite. • Ex. NO3-  Nitr-ate Ion NO2-  Nitr-ite Ion • The Prefix per- indicates one more atom than the ion ending in –ate. • The Prefix hypo- indicates one fewer atom than the ion ending in –ites.

  7. Chemical Nomenclature • Tips & Tricks for naming anions: (Part Two) • Anions derived by adding H+ to any oxyanion are named by adding as a prefix the word hydrogen or dihydrogen, as appropriate. • Ex. • PO43- phosphate • HPO42- hydrogen phosphate • H2PO4- dihydrogen phosphate • Names of ionic compounds consist of the cation name followed by the anion name • Ex. NaCl Sodium Chloride

  8. Structuring Q : The Charge A : Mass Number Z : Atomic Number

  9. Percentage Compostitions Formula Weight: Sum of the atomic weights of each atom in its chemical formula. Example:Calculate the percentage of carbon in C12H22O11. Atomic Weight of Carbon:12.0 amu Addition of Atomic Weights:12 C atoms = 12 (12.0 amu) = 144.0 amu22 H atoms = 22 (1.0 amu) = 22.0 amu11 O atoms = 11 (16.0 amu) = 176.0 amu 342.0 amu

  10. Avogadro’s Number • Named after Amedeo Avogadro (1776-1856) • NA = 6.02 x 1023 atoms / 1 mol • 1 mol ‘Element’ = 6.02 x 1023 atoms • 1 mol ‘Compound’ = 6.02 x 1023 molecules • 1 mol ‘Ions’ = 6.02 x 1023 ions

  11. Limiting Reactants • Limiting Reagent: Determines, or limits, the amount of product formed. • Left over reactants are often called excess reactants. • Theoretical Yield: Quantity of product calculated to form • Actual Yield: Quantity of product actually obtained

  12. Gases • Standard temperature and pressure (STP) is 273.15 K and 1 atm. • 1 atm = 760 mm Hg = 760 torr = 101.325 kPa • Boyle’s Law: States that the volume of a fixed quantity of gas maintained at constant temperature is inversely proportional to the pressure. • PV = constant • Charles’s Law: States that the volume of a fixed quantity of gas maintained at a constant pressure is directly proportional to the absolute temperature. • V / T = constant

  13. Gases • Avogadro’s Hypothesis: Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules. • Avogadro’s Law: states that the volume of a gas maintained at constant temperature and pressure is directly proportional to the number of moles in the gas. • V / n = constant

  14. Ideal Gas Law • The ideal-gas equation is… PV = nRT. • R is the gas constant. • R=8.314 J/molK R=0.08206 Latm/molK • Remember! Temperature is in Kelvins, not degrees Celsius.

  15. More About Gases • If n and T are constant, the values of P and V can change, but the product of PV must remain constant, so: • P1V1=P2V2 • When just n is constant, P,V, and T can all change but the product of (PV)/T must remain constant so: • (P1V1)/T1=(P2V2)/T2  Often called the combined gas law

  16. Partial Pressure • The total pressure of a mixture of gases equals the sum of the pressures that each would exert if it were present alone: • Pt = P1+P2+P3 • Each gas in a mixture behaves independently so we can relate the amount of a given gas in a mixture to its partial pressure: • P1 / Pt = (n1RT/V) / (ntRT/V) = n1/ntmole fraction • P1=(n1/nt)Pt

  17. Graham’s Law and rms Speed • Particles with lighter masses have a higher rms speed. • u= M is molar mass • Graham’s law states that if we have two gases at the same temperature and pressure in containers with identical pinholes, and r is the rate of diffusion, then: • r1/r2=

  18. Van der Waals • Van der Waals recognized that the ideal gas equation could be corrected to account for the effects of attractive forces between gas molecules and for molecular volumes. • Constant a is a measure of how strongly the gas molecules attract each other and constant b is a measure of the small but finite volume occupied by the gas molecules themselves. • (P+(n2a)/V2)(V-nb)=nRT

  19. Thanks to… Chemistry: The Central Science by T. Brown, H. LeMay, B. Bursten, and C. Murphy

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