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Chemistry, Chapter 6 - H2O =-1726J q endo =-q exo = 1726kJ...

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Finish Chapter 6 K/T/W. Read “Chemistry of Fuels/Energy Sources” pp. 283-293. Begin Chapter 7. Atomic Structure. I. Electromagnetic Radiation (Transverse Waves) C = γ*r where C = 3.0*10^8 m/s a. Entire spectrum b. Visible spectrum c. Traveling waves versus standing (stationary) waves II. Black Body Radiation (Planck 1900) a. Heating metal to high temp. b. Emitted radiation vs. quantized (discrete particles of energy) quanta . c. E = h*r = h*c/γ III. Dual nature of light. Has both properties of waves (diffraction) and particles (photoebrotic effect, Einstein, 1905) IV. Continuous light spectrum vs. line emission spectra. Within given phase q = (specific heat capacity)(mass)(t f -t i ) J = (J/g-°C)(g)(°C) q endo + q exo = 0 q endo = -q exo Problems : 2. Given that 20g of NH 4 NO 3 (s) added to 250mL of H 2 O(l) at 22.15°C lowers temp. to 20.50°C (cold pack), (1) calculate heat given up by H 2 O(l), q exo (2) calculate q endo in J/mole absorbed by dissolving NH 4 NO 3 (s) in H 2 O(l). 2) q exo = q H2O = (4.184 J/g-°C)(250mL x 1.0 gH 2 O/mL)(20.50°C – 22.15°C) q exo = q H2O = -1726J
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Unformatted text preview: H2O = -1726J q endo = -q exo = +1726kJ xmoles NH 4 NO 3 = 20g NH 4 NO 3 * 1mol/80g = 0.25 moles NH 4 NO 3 q endo = +1726kJ/0.25mol NH 4 NO 3 = 6900 J/mol NH 4 NO 3 4. Three metal blocks (Cu(s), Pb(s), Al(s)), each of mass 827g, of temp. 82.6°C, are added separately to 600Ml H 2 O(l) at 20.0°C in each of three beakers. (a) calculate specific heat capacity of Cu(s) if final experimental temp. is 26.6°C. (a) q exo = q Cu(s) = (x * J/g-°C)(827g)(26.6°C – 82.6°C) q exo = -46312x q endo = q cold H2O = (4.164 J/g-°C)(600g)(26.6°C-20.0°) q endo = -q exo solve for x = x = C Cu(s) = .357 J/g-°C (b) Given that C Pb(s) = 0.128 J/g-°C, calculate final temp. (t f ) (b) q exo = q Pb(s) = (0.128 J/g-°C)(827g)(t f – 82.6°C) q endo = q cold H2O = (4.184 J/g-°C)(600g)(t f -20.0°) solve for t f , t f = 22.5°C (c) State basic assumption in working three problems. (c) C Cu(s) = .385 J/g-°C C Al(s) = .90 J/g-°C C Pb(s) = .128 J/g-°C C H2O(l) = 4.184 J/g-°C...
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