Chapter 4 -lecture 5

Chapter 4 -lecture 5 - General Chemistry I Fall 2007 Joann...

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Unformatted text preview: General Chemistry I Fall 2007 Joann S. Monko Chemistry 9th ed. Raymond Chang The reaction of potassium carbonate and copper (II) iodide... __ K2CO3 (aq) + __ CuI2 (aq) 0 The reaction of potassium phosphate and magnesium nitrate... __ K3PO4 + __ Mg(NO3)2 The reaction of hydrochloric acid and sodium sulfide... 2 HCl (aq) + Na2S (aq) --> H2S (g) + 2 NaCl (aq) Net: The reaction of hydrochloric acid and strontium carbonate... 2 HCl (aq) + SrCO3 (s) --> SrCl2 (aq) + H2O (l) + CO2 (g) Net: The reaction of ammonium chloride and lithium hydroxide... __ NH4Cl (aq) + __ LiOH (aq) Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. GasForming Reactions This is primarily the chemistry of metal carbonates. MCO3 + acid ---> CO2 + salt +H20 CaCO3 (s) + 2 H+ (aq) ---> H2CO3 (aq) + Ca2+ (aq) H2CO3 (aq) ---> CO2 (g) + H2O (l) Other gases form from: metal sulfides, metal sulfites, & ammonium salts. H2S SO2 NH3 Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. The Nature of Acids An acid -------> H+ in water HCl (aq) H2O + HCl H+ (aq) H3O+ + + Cl- (aq) Cl- Strong Acids dissociate 100%. HCl H2SO4 HClO4 HNO3 hydrochloric sulfuric perchloric nitric HCl ClH3O+ H2O The Hydronium Ion Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. (Strong Electrolytes) Weak Acids WEAK ACIDS = weak electrolytes CH3CO2H H2CO3 H3PO4 HF acetic acid carbonic acid phosphoric acid hydrofluoric acid Acetic acid Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Acids Nonmetal oxides can be acids CO2 (aq) + H2O (l) ---> H2CO3 (aq) SO3 (aq) + H2O (l) ---> H2SO4 (aq) and can come from burning coal and oil. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Bases NaOH (aq) Base ---> OH- in water ---> Na+ (aq) + OH- (aq) NaOH is a strong base 100% ionization Strong electrolyte Metal oxides are bases CaO (s) + H2O (l) Ca(OH)2 (aq) CaO in water. Indicator shows solution is basic. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. 3 Ammonia, NH An Important Base Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Know the strong acids & bases! Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. AcidBase Reactions The "driving force" is the formation of water. NaOH (aq) + HCl (aq) ---> NaCl (aq) + H2O (l) Net ionic equation OH- (aq) + H+ (aq) H2O (l) For ALL rxtns of STRONG acids and bases. A-B rxtns A.K.A. NEUTRALIZATIONS -the solution is neither acidic nor basic at the end. Other product of the A-B rxtn is a SALT, MX. HX + MOH ---> MX + H2O n+ Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. The pH Scale pH = log (1/ [H+]) = - log [H+] In a neutral solution, [H+] = [OH-] = 1.00 x 10-7 M at 25 oC pH = - log [H+] = -log (1.00 x 10-7) = - (-7) = 7 Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. [H+] and pH If the [H+] of soda is 1.6 x 10-3 M, the pH is ____? Because pH = - log [H+] then pH= - log (1.6 x 10-3) pH = - (-2.80) pH = 2.80 Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. pH and [H+] If the pH of Coke is 3.12, it is ______. Because pH = - log [H+] then log [H+] = - pH Take antilog and get [H+] = 10-pH [H+] = 10-3.12 = 7.6 x 10-4 M Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Clicker Question Which statement is NOT Correct? A. pH = 1.89 is equal to [H+] = 1.29 x 10-2 M B. pH = 4.55 is equal to [H+] = 2.82 x 10-5 M C. pH = 7.38 is equal to [H+] = 4.17 x 10-8 M D. pH = 8.95 is equal to [H+] = 7.85 x 10-9 M E. pH= 11.05 is equal to [H+]= 8.91 x 10-12 M Importance of Gases - Common elements/compounds exist as gases. Others can be vaporized. Table 5.1 - Our atmosphere duh! - Gases can be described/explained using simple mathematical models. Airbags fill with N2 gas. Gas is generated by the decomposition of sodium azide, NaN3. 2 NaN3 ---> 2 Na + 3 N2 Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. General Properties of Gases There is a lot of "free" space in a gas. Can be expanded infinitely. Occupy containers uniformly/completely. Diffuse and mix rapidly. Have much lower densities than l & s. Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Properties of Gases Gas properties can be modeled using math. Model depends on-- V = volume of the gas (L) T = temperature (K) n = amount (moles) P = pressure (atmospheres) STP = standard temperature and pressure = 273 K (0 C) and 1 atm Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Pressure of air is measured with a BAROMETER (Torricelli in 1643) Hg rises in tube until force of Hg (down) balances the force of atmosphere (pushing up). P of Hg pushing down related to Hg density column height Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Pressure Pressure Column height measures P of atmosphere 1 standard atm = 760 mm Hg (exactly) 29.9 inches 1.01325 bar SI unit is PASCAL, Pa, where 1 atm = 101.325 kPa Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Figure 5.4 Chemistry, 8th ed. Chang Figure 5.5 Chemistry, 8th ed. Chang Boyle's Law "Compressibility" If n and T are constant, then PV = k = (nRT) P 1/V P goes up as V goes down. As the volume of the air trapped in the pump is reduced, its pressure goes up, and air is forced into the tire. P 1 V 1 = P2 V 2 at constant n & T Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Boyle's Law P x V = Constant P1 x V1 = P2 x V2 Amount & Temperature are NOT changed. Figure 5.7 Chemistry, 8th ed. Chang At 0 C and 5.00 atm, a given sample of gas occupies 75.0 L. The gas is compressed to a final volume of 30.0 L. What is the final pressure? P1V1 = P2V2 P1 = 5.00 atm P1V1 = P2 V2 P2 = ? at constant n & T V1 = 75.0 L V2 = 30.0 L ( 5.00 atm ) ( 75.0 L ) = P2 ( 30.0 L ) P2 = 12.5 atm Kotz &Treichel Chemistry & Chemical Reactivity 5th ed. Clicker Question An airbag containing 65.0 L of N2 had a pressure of 745 mm Hg. The gas was transferred to a 25.0 L container. Temperature and moles remained constant. What is the pressure in the new container? a. 1940 mm Hg b. 287 mm Hg c. 11.5 mm Hg d. 2.18 mm Hg e. 458 mm Hg ...
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