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chem notes 10-15

# chem notes 10-15 - -individual gas types do not interact...

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October 15, 2007 Dr. Stevens Gen. Chem. 1 Test Wednesday -review Tues. night -given on test: R values -chapter 4, 12, 5 Applications of Gas Equations/Relationships -ex: Calculate density of N2 at 20C and 1atm -d = m/v = g/L => moles/vol = n/v -n/v = P/RT =>1/293(0.08206) x 28/1 = 28/293(0.08206) = 1.2g/L -ex: Calculate MM of an unknown gas for which 2.0g is placed in 1.0L at STP. -MM = g/mol = mass/n -MM = 2.0g/n -n = PV/RT = 1(1)/0.08206(273) = 0.045mol -2.0/0.045 = 45g/mol Stoichiometry and Gas Relations -ex: If 2.0g CaCO3 is reacted with excess HCl according to: CaCO3 + 2HCl CaCl2 + H2O + CO2, calculate p if 50.0mL of a test tube is used at 23C. -V = .05000L -P of CO2 -P = nRT/V -2.0g/100 = .020mol -P = .020(0.08206)(296)/.050 = 9.7atm Dalton’s Law of Partial Pressures: -PV = nRT -Partial Pressure: P of an individual gas component in a mixture -Total P of a mixture = sum of individual PP b/c each gas exerts P as if it is alone in the flask -idealized assumption

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Unformatted text preview: -individual gas types do not interact with each other = very idealized-in the same flask-P and n are variables in Dalton’s Law-PV = nRT-P/n = RT/V = C- P1/n1 = C, P2/n2 = C-P1/n1 = P2/n2-ex: The total P of 1.0mol NO 1.5mol H2O = 8.0atm. Calc. PP of NO and H2O-P(no)/n(no) = P(h2o)/n(h2o) = P/n-P(no)/1 = P(h2o)/1.5 = 8.0atm-P(h2o)/1.5 = 8.0/2.5 = 4.8atm-Pno = 8.0 – 4.8 = 3.2atm Real Gases:-when P and V are NOT ideal-if P and V are not ideal, we cannot correctly use PV = nRT-most ideal P is low, V is large-no interaction-intermediate situation attractive forces (imf) as molecules approach at intermediate P and V-molecules cluster together (if n decreases, P drops as well)-Pideal = P an^2/v^2-large a for large imf-H2O v. He a(h2o)>a(he)-extreme situation P is high, v is small-NOT ideal-Videal = (V(real)-nb(#mole)) b = measure of size-Ideal: PV = nRT-Real: (P + an^2/v^2)(V-nb) = nRT...
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