CHEM LLz

Thermalsnergryr and Phase Ghanges

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ETAMPLE: How m1lh total energy does it take to convert 40.0 g of ice at -.30oC to steam at l2S oC?D.atE .y.pu.nsed tg knqw:AHn'. s ggg llg AH.*ap = 2gSA!/gCi** a f,,06 Ilg*C C**to = {. tS y/gdCHeat ice to rnelting point

Q_= Tn 'e , .Nf' 40J' t,# . (O.C + 3ot") : TqqL TMelt ice Yt

q= AHr.*.,14 = ry, ,-.lo,OJ = l332OSHeat water to boiting point t'

1= ?n,c ./.f "- '{OJ,tdry , ('*'C - 0"c)= ltaTTDfVaporize water \

t= Aft" np""fr= /e5to5$' tlog = lor+o5Heat steam to te$ oC

Q : rn ,f , a:r F t{t},Oq ., }$"t"f ,L 'll \* r->' J W.J

C*t*a* = l.ge J/g*C

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h-t6*} lcs and fiquid wnter{melting}

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CHEM LLz |anuary 27,2AIA

$lickef Ouestion:S0g of ethanol is at 20oC. I add 6385J of heat. What is the frnal temperatureand state of the ethanol? (Tup=?g.4oC, Ce.ohE l.4$/g-oC, Afloo=g3i.ayg>

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CHEM LLz

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Hesst lrawF Enthalpy is a state function.) rf a reaction can be rwitten as the sum of two or more

reactions, the AH for the net reaction is the sum of theAH's for the individual steps.

> rf a reaction is reversed, the sign of AH is reversed.F If the coefficients of the reactants/products are multiplied

by a number, then the AH must be multiplied by thatnumber, as well.