Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20General Chemistry Topic 5:GasesObjectives: By the end of this topic, you should:1. Understand the general idea of the gaseous state.2. Be able to describe the behavior of gases as expressed by the gas laws – Boyle’s Law, Charles’ Law, Avogadro’s Law, and the Combined Gas Law. 3. Be familiar with the concept of gas pressure, partial pressures, and units of pressure measurement. 4. Be able to do simple gas law calculations. Suggested reading: Denniston et al., Chapter 5, pp. 171-184 (165-180), Summary on p. 196 (189)Homework problems: 5.40 (5.36), 5.47 (5.43), 5.57 (5.53), 5.63 (5.59)We need some basic knowledge about the behavior of gases•relevant to many chemical Rx•relevant to physiological function•O2 and CO2•respiratory gas exchange (breathing and in tissues) “blood gases”GasesProperties/Behavior of GasesKinetic Theory of Gases:1. A gas is composed of very small particles. 2. Gas particles are very far apart (mostly empty space).3. Gas particles move rapidly, colliding with the walls of any container (pressure) and with each other.4. Gas particles don’t repel or attract each other.5. Gas particles move faster when temperature increases(more thermal energy).Barometer measures gas pressureAtmospheric (barometric) pressure isthe force of gases in the atmosphere pressing down against us: - 1 atm - 760 mm Hg - 1 kg/cm2Sea levelTop of Mt. Everest9300 m (29,029 ft)273 mm HgDouble the pressure;decrease volume by 1/2Double the temperature (K);double the volumeBoyle’s LawPressure and volume of a gas are inversely related(when one gets smaller,the other gets bigger)Charles’ LawVolume of a gas is directlyrelated to temperature (K) at constant pressure(when one gets bigger,the other gets bigger, and vv)Gas LawsGay-Lussac’s LawPressure of a gas is directly related to temperature (K) at constant volume(when one gets bigger,the other gets bigger, and vice versa)Double the temperature;double the pressure(if volume doesn’t change)Equal volumes of gases, at the same temperature andpressure, contain the same number of moleculesDouble the amount (# of moles) of a gas:Volume will double (at constant T & P)Avogadro’s Law: Volume and moles of a gasMolar volume: Under standard conditions (0C, 1 atm),1 mole of any gas occupies a volume of 22.4 L.= 0C1 mole He1 mole O21 mole N2PHe = 2.0 atmPAr = 4.0 atmPtotal = PHe + PAr = 2.0 atm + 4.0 atm = 6.0 atm Dalton’s Law: partial pressures of gases in a mixtureIn a gas mixture (e.g., air, blood), each gas exerts its partial pressure, the pressure it would have if it was the only gas in the container. Total pressure of a gas mixture = sum of all the partial pressures of the gases in the mixtureHeAr He + Ar mixtureHenry’s Law: gases dissolved in a liquidAmount of gas dissolved in a liquid depends on the pressure of the gas above the liquid. More pressure = more gas in the liquid.closedopenhi pressure CO2“carbonated”Not a trivial consideration – gas exchange in: - lungs (breathing O2 in, waste CO2 out) - blood/tissues (O2 out, waste CO2 in) depends on pressure differencesCombined Gas Law: pressure, volume, temperatureAll the pressure, volume and temperature relationships can be combined into a single relationship called the combined gas law.If the amount of a gas (number of moles) remains constant:PiViTiPfVfTf=InitialconditionsFinalconditionsIf you know all the initial conditions and any two of the final conditions, you can calculate the third.Keep in mind how volume and/or pressure change when you change the amount of gas (# of moles).1 mole of any gas has a volume of 22.4 L under standard conditions (0C, 1 atm).Kinetic theory of gases (general idea)BarometerPressure of a gasAtmospheric pressureDo you know how pressure, temperature, and amount of gas affects volume, and/or how changing volume affects the above? Boyle’s Law (and how to apply it in practice) Charles’ Law (and how to apply it in practice) Avogadro’s Law (and how to apply it in practice)Molar volume of a gas (22.4L)Total gas pressure vs. partial pressureCombined gas law – can you use it to predict gas behavior?VocabularyYou should know the meaning of the following termsGeneral Chemistry Topic 6:Chemical Reactions & EquationsObjectives: By the end of this topic, you should:1. understand the concept of the mole, and appreciate its importance in chemical reactions.2. be able to write simple chemical formulas, balance simple chemical reactions, and do simple quantitative calculations involving chemical reactions. 3. know how to calculate molecular/formula weights, and how to convert grams to moles. 4. know (memorize) Avogadro’s number, and appreciate its significance. Suggested reading: DTC, Chapter 4, pp. 137-165 (136-161) Homework problems: 4.69 (4.71), 4.71-4.72 (4.73-4.76), 4.102 (4.86), 4.105 (4.89)Chemical EquationChemical ReactionsPhysical change – appearance of a substance is altered (but not its composition) e.g., boiling water, melting ice, sawing wood, “Breaking rocks in the hot sun”Chemical change – something changes into a new thing (different composition) e.g., rusting nail, burning methane or gasoline oxidizing food to stay aliveChemical Reaction – atoms of reacting substances form new combinations with new physical properties Carbon + Oxygen = Carbon DioxideC + O2 CO2Balancing Chemical EquationsH2 + Cl2 HClunbalancedbalancedH2 + Cl2 2 HClOxidation of methane(gas stove)CH4 + O2 CO2 + H20CH4 + O2 CO2 + H2022unbalancedbalancedTry this at home: Balance the equations belowNa + Cl2 NaClCu2O + O2 CuOAl + O2 Al2O3Na + Cl2 + O2 NaClO4C4H8 + O2 CO2 + H20Al + Cl2 AlCl3Mg + AgNO3 Mg(NO3)2 + AgCaCO3 CaO + CO2HgO Hg + O2Chemical Rx: molecules, moles, gramsC + O2 CO2Consider the chemical Rx:+We can read the equation for this reaction several ways:1 atom of carbon and one molecule of oxygen react to form one molecule of carbon dioxide1 mole of carbon and one mole of oxygen react to form one mole of carbon dioxide12.0 g of carbon and 32.0 g of oxygen react to form 44.0 g of carbon dioxide (molar masses)6.02 x 1023 atoms of carbon and