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Stoichiometry and Gases

Stoichiometry and Gases. By Alec “Dr. Bathroom” Levy Niteesh “The Yellow Dart” Chitturu. Nomenclature. Cation-Electron-deficient atom/molecule (+ charge) Atoms in transition metals, alkalines, alkaline earths typically form cations Ex.: Ca 2+ Fe 2+ Li +

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Stoichiometry and Gases

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  1. Stoichiometry and Gases By Alec “Dr. Bathroom” Levy Niteesh “The Yellow Dart” Chitturu

  2. Nomenclature • Cation-Electron-deficient atom/molecule (+ charge) • Atoms in transition metals, alkalines, alkaline earths typically form cations • Ex.: Ca2+ Fe2+ Li+ • Transition metals include Roman Numerals except Zn2+ Ni2+ Ag+ • Anion-Electron-surplus atom/molecule (- charge • Form in halogens, chalcogens, pnictogens, and polyatomic molecules • Ex: F- O2- N3- SO2-

  3. Nomenclature • Atom-smallest unit of element that retains its properties, includes mono- and poly- • Compound-2 different elements bonded together • Molecule-Covalently bonded atoms • Salt-Combination of 2 or more ions bonding to form a neutral compound • Same thing as a neutral ionic compound, which consists of a metal cation and nonmetal anion

  4. Acid Nomenclature • Acids-Contains H+ cation • -ide hydro_____ic acid • -ate _____ic acid • -ite ______ous acid • Ex: Sulfide=hyrdosulfuric acid • Ex: Sulfate=sulfuric acid • Ex: Sulfite=sulfurous acid

  5. Bonding & Formulas • Covalent compounds-2 or more nonmetals, come first in formula, except for F and O • Organic compounds-Hydrocarbons, consists of only C and H • Alkanes-Carbon backbone, fills in excess with H, ends with –ane 1=meth 2=eth 3=prop 4=but 5+=binary • Alcohols-Adds O to chain, ends in -anol

  6. Common Anions • 1-H- (Hydride ion), F- (Fluoride ion), Cl- (Chloride Ion), Br- (Bromide ion), I- (Iodide ion), CN- (Cyanide ion), OH- ( Hydroxide ion), C2H3O2- (Acetate ion), ClO3- (Chlorate ion) ClO4- (Perchlorate ion), NO3- (Nitrate ion), MnO4- (Permanganate ion) • 2- O2- (Oxide ion), O22- (Peroxide ion), S2- (Sulfide ion), CO32- (Carbonate ion), CrO42- (Chromate ion), Cr2O72- (Dichromate ion), SO42- (Sulfate ion) • 3- N3- (Nitride ion), PO43- (Phosphate ion)

  7. Atomic Structures • Angstrom-Å=10-10 meters=size of an atom • Proton-Subatomic particle with positive charge of 1, in the nucleus • Neutron-Subatomic particle with neutral charge, in the nucleus • Electron-Subatomic particle with negative charge of 1, in energy orbitals • Protons and Neutrons consist of 99.99% of mass • 1 electron=1/1800 proton

  8. Isotopic Notation X A q • Isotopes have same number of protons but different number of neutrons and are chemically identical • A-Mass number=protons+neutrons • q-Charge=electron+protons • Z-Atomic number=protons Z

  9. Isotopic Abundance/Molar Mass • To calculate isotopic abundance from molar mass • Ex: Average mass of sample is 1.614 g/mol. Molar mass of hydrogen-1 is 1.00782, molar mass of deuterium is 2.01410. What is the abundance of the two isotopes? • Answer: hydrogen-1=39.76%, deuterium=60.24%

  10. Balancing reaction equations • Given: C24H46O3 + O2CO2 + H2O • Answer : C24H46O3 + 34O224CO2 + 23H2O It’s 1.5-glyceride Isn’t Chemistry pHun?

  11. Mass-mole relationship • 1 mole of a substance is equal to 6.022 x 1023 particle • 1 mole of substance is equal to its amu but in grams • Poly-atomic substances moles are a sum of its constituents • Ex: C24H46O3 has 24 C, 46 H, and 3 O. Thus: (12.0107 x 24) + (1.00794 x 46) + (15.9994 x 3)=382.62024 g/mol

  12. Empirical formulas/percent composition • Given percent composition by mass spectrometry, the empirical formula of a molecule is what? • 54.50% carbon, 13.72% hydrogen, 31.78% nitrogen • Assume given values are in grams, then calculate for moles • Divide moles by lowest value of moles • Answer is subscript of empirical formula • To determine molecular formula, molar mass must be known Ex: 88.15 g/mol

  13. Limiting/Excess Reactants • To determine limiting reactant, balance equation and solve for both reactants • Lower value is limiting, the higher one is excess

  14. Percent Yield • Percent Yield=(actual or experimental value)/(theoretical values determined by limiting reactant) Easy? Yes/No?

  15. IT’S A GAS GAS GAS!!! • Qualitative: pressure, volume, number of moles, and temperature are at work, along with R, the gas constant • Boyle’s Law: Volume of gas at constant temperature is inversely proportional to pressure V=k ∙ 1/p • Charles’s Law: Volume of gas at constant pressure is directly proportional to absolute temperature V=k ∙ T • Avogadro’s Law: Equal volumes of gases at equal temperature and pressure contains equal number of molecules, and volume of gas at constant pressure and temperature is directly proportional to number of moles V=k ∙ n

  16. Ideal Gas Law • PV=nRT • R is the ideal gas constant, equal to 0.08206 L-atm/mol-K • Volume of a gas at STP is 22.41 L • To calculate density, calculate concentration (mol/L) and convert to g/cm3 (1 mL=1 cm3)

  17. PV=nRT in action… • Given: pressure is 1020 torr, volume is 1.5 L, and temperature 37. 4 degrees Celsius, mass of sample is 2.530 g, what is the molar mass? • 1020 torr=1.342 atm • 37.4 degrees Celsius=310.55 degrees Kelvin • n=PV/RT=.07899 mol • Molar mass=g/mol=2.530 g/ .07899 mol= 32.03 g/mol • It’s O2!

  18. Partial Pressure • Dalton’s law of partial pressures: Total pressure of a mixture of gases equals the sum of the pressures that each would exert alone • Applies only for ideal gases!!! • Pt = P1 + P2 + P3 …. + Pn • Mole fraction (X)=Moles of given gas/Total Moles of gas • Pn = Xn Pt

  19. Kinetic Molecular Theory • Gases consist of large amounts of molecules in continuous random motion • The molecules have negligible volume compared to the total volume the gas occupies • There are negligible attractive or repulsive forces between those molecules • The average kinetic energy of the molecules remains constant (the collisions are perfectly elastic) • The molecule’s average kinetic energy is proportional to the absolute temperature

  20. Root Means Square Speed • Velocity=u=√(3RT/M) • R=gas constant • T=absolute temperature • M=kg/mol • Lighter molecules move on average faster than heavier molecules

  21. Graham’s rates of effusion/diffusion • Effusion: Gas escaping into a vacuum • Diffusion: Gas mixing into another gas, going from high concentration to low concentration • Rate A escapes/Rate B escapes= ua/ub = √Mb/Ma

  22. Van der Waals’s equation • Real (non-ideal) gas equation • Molecules DO occupy space, thus takes up volume • Molecules DO sometimes attract each other • Correction factors are needed • (Preal + a(n/v)2)(Vcontainer – bn)=nRT • a=attractive coefficient, expressed in atm ∙ L2/mol2 • b=volume coefficient, expressed in L/mol (Das Good?)

  23. Fin Dr. Bathroom and the Yellow Dart…Away!?!

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