CHEM 150 1st Edition Lecture 13 Outline of Last Lecture • Exothermic Reaction• Endothermic Reaction • Heat and Work• Boiling water Outline of Current Lecture • PV work• Specific heat• EnthalpyCurrent LectureQ: If a gas pushes a piston against a constant pressure of 1.200 atm. The volume of the gas changes from 1.250 L to 3.460 L. What is w?A: W=-PΔV -1.200atm (4.360L - 1.550L) x 101.325J/101.23-268.7139JQ: If the gas loses 132.5 J of heat energy int this process, what is ΔE for the gas?A: ΔE= -132.5J - 268.75-401.2J• Calculating energy changes from temperature changesq = Cs.m.ΔTCs : specific heat (specific heat capacity)water: Cs = 4.184 J/gECcopper: Cs = 0.387 J/gECQ: How much heat energy is required to raise the temperature of 100.0g of water from 25.00C to100.00C?A: q=4.184J/gC x 100g x (100.00C-2500C) = 31.38KJ or 3.138x10^4J• Enthalpy(H) ΔH = q at constant pressureThermochemical equations: equations that include the enthalpy of the reaction.2C2H6(g) + 7O2(g) ------> 4CO2(g) + 6H2O(g) ΔH= -2855.58KJQ: Is this reaction endothermic or exothermic?A: This reaction is exothermic. Q: How much heat energy can be obtained by burning 1.000 mole of ethane?A: 1.000 of C2H6 x 2855.58KJ/ 2mol C2H6 =1427.79KJQ: What is the enthalpy change if 60.00g of oxygen are consumed in the combustion of ethane?A: 60.00g O2 x 1mol O2/32.00g x -2855.586J/ 7mol O2=
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