PRIMERA LEY DE LA TERMODINÁMICA 1.
Una vasija vasija vacía vacía pesa pesa 3 kp. Llena e a!"a a!"a pesa pesa #3 kp $ llena llena e !lice !lice%ina %ina pesa pesa && kp. 'alla% 'alla% la ensia ensia %ela(i %ela(iva va e la la !lice%ina.
2.
&) !%a*+s e +,í!en+- !as e c+*p+%(a*ien(+ ieal- %ealia "n (%a/aj+ e 3.# k0 s+/%e l+s al%ee+%es al e,pani%se is+(%*ica*en(e a "na p%esi2n inal e 1.4 a(* $ "n v+l"*en inal e 54 *3. De(e%*ine el el v+l"*en inicial 6"e +c"pa +c"pa el !as. {5 litros}
3.
'alla% el (%a/aj+ 6"e 7a$ 6"e s"*inis(%a% a "n !as pa%a c+*p%i*i%l+ ese "n v+l"*en e 34 l a 1 a(* 7as(a "n v+l"*en e 3 l- pe%*anecien+ c+ns(an(e la p%esi2n. {6 990 J}
4.
En "n p%+ces+ %eve%si/le a 5# +C- se %e"ce la p%esi2n p%esi2n s+/%e 1.4 *+les e !as 7eli+ ese 14 a(* a 1.4 a(*. Calc"la%8 9: ;: U $ '. {Q = 1 372 cal}
5.
3.4 ! e !as 7i%2!en+ se enc"en(%an enc"en(%an /aj+ la p%esi2n e #.4 a(* a la (e*pe%a("%a e 4.4 +C. Desp"s e "na e,pansi2n a p%esi2n c+ns(an(e el !as +c"pa "n v+l"*en e 1# l. Calc"la%8 ;- 9<- U- 9P $ '. {W = −1 002 cal; ∆U = 2 530 cal}
6.
Calc"le el (%a/aj+ *íni*+ necesa%i+ pa%a c+*p%i*i% 54 ! e O 5 ese 14 7as(a 7as(a #.4 li(%+s li(%+s a 4.4 =C. C">n(+ C">n(+ cal+% se !ene%a en el p%+ces+. Ta*/in calc"la% calc"la % U $ '. {−Q = W = 235 cal}
?.
Calc@l Calc@lese ese U pa%a pa%a "n "n ca*/ ca*/i+ i+ e es(a+ es(a+ en el 6"e 1.4 *+l e '5O pasa e 5# +C $ 1.4 a(* a 34 +C $ 1.4 a(*. C+nsi%ese C+nsi%ese "n p%+ces+ e calen(a*ien(+ %eve%si/le a 1.4 a(*. {∆U aproximaam!"t! 90 cal}
.
Be ejan ejan e,pani% e,pani% is+(%*ic is+(%*ica*en( a*en(ee #.4 *+les *+les e "n !as ieal ieal ia(2*i ia(2*ic+c+- a 5#= 5#= C- ese ese 4.4544 4.4544 a 4.1444 4.1444 *3 . Calc"le8 9;- U $ '- c"an+ la e,pansi2n se eec(@a a %eve%si/le*en(e%eve%si/le*en(e- $ / is+/>%ica*en(e- c+n(%a "na p%esi2n c+ns(an(e e ∆ 1.44 a(*. {#. Q = $.10 %J; & = 0 cal}
.
La capacia capacia cal2%ica cal2%ica el el ai%e a (e*pe%a( (e*pe%a("%a "%a a*/ien(e a*/ien(e $ 1.4 a(* e p%esi2 p%esi2n n es *>s *>s + *en+s *en+s 51 0 F1 *+lF1. C">n(+ cal+% se necesi(a pa%a calen(a% "n c"a%(+ vací+ en 14 inicial*en(e a (e*pe%a("%a (e*pe%a("%a a*/ien(e. Bea la i*ensi2n el c"a%(+ c"a%(+ # * , # * , 3 *. Desp%ecian+ Desp%ecian+ las p%ias e cal+%- c">n(+ c">n(+ (ie*p+ le (+*a%> a "n calen(a+% e 1.4 k; calen(a% el c"a%(+ en la *is*a can(ia. G&&) se!"n+sH
10.
Bi "n k! e a!"a es evap+% evap+%a+ a+ en "n %ecip %ecipien ien(e (e !%ane !%ane +ne +ne la p%esi2 p%esi2n n es e 4.1 a(*. Ba/ien Ba/ien+ + 6"e 'ev a la (e*pe%a( (e*pe%a("%a "%a e e/"llici2n e/"llici2n el a!"a )& =C a esa p%esi2n p%esi2n es )) k0J*+l. Bi el cal+% "e s"*inis(% s"*inis(%a+ a+ elc(%ica* elc(%ica*en(e en(e-KC">n(+ KC">n(+ cal+% e/e aplica%se aplica%se $ 6" p+(encia p+(encia el calen(a+% calen(a+% en a((s se %e6"ie%e %e6"ie%e pa%a la evap+%aci evap+%aci2n 2n (+(al en 14 *in"(+s KDese 6" al("%a e/e cae% cae% "na *asa e 14 k! pa%a ap+%(a% la ene%!ía ene%!ía %e6"e%ia {Q = 2442 2442 %J; 4.07 %W; 249 %m}
11. C"an+ C"an+ 7ie%ve el a!"a a!"a a la p%esi2n p%esi2n e +s a(*2se% a(*2se%as as el cal+% e vap+%i vap+%iaci2n aci2n es )& TUJl/: TUJl/: el p"n(+ p"n(+ e e/"llici2ne/"llici2n- 5#4 + : 1 l/ e vap+% +c"pa "n v+l"*en e 1) pies 3- $ 1 l/ e a!"a- "n v+l"*en e 4.41? pies3. a. Calc"la% en li/%asFpie $ en (" el (%a/aj+ (%a/aj+ e,(e%n+ e,(e%n+ c"an+ se +%*a "na li/%a e vap+% a es(a (e*pe%a( (e*pe%a("%a. "%a. . Calc"la% Calc"la% en (" el a"*en(+ a"*en(+ e ene%!ía in(e%na. 12.
Be c+*p%i*e aia/>(ica*en(e a%!2n !ase+s+- inicial*en(e a 54 =C $ a p%esi2n a(*+s%ica- a "na 6"in(a pa%(e e s" v+l"*en inicial. Calc"le la p%esi2n p%esi2n $ la (e*pe%a("%a el !as c+*p%i*i+. c+*p%i*i+. {$56 '}
13.
Be *an(ienen *an(ienen &# !%a*+s e ,en2n a "n %ecipien( %ecipien(ee e 5.4 a(* $ (e*pe%a("% (e*pe%a("%aa a*/ien(e. a*/ien(e. En(+nces En(+nces se le pe%*i(e e,pani%se aia/>(ica*en(e8 a %eve%si/le*en(e %eve%si/le*en(e a 1.4 a(*- / c+n(%a 1.4 a(* e p%esi2n. p%esi2n. Bi la (e*pe%a("%a inicial es es 5 - c">l se%> la (e*pe%a("%a (e*pe%a("%a inal en caa cas+. C< ,en2n es 54.? 0J *+l. {245 '; 255 '}
1
14.
Pa%a "n cie%(+ !as ieal e Cp .# calJ *+l. Bi 5.4 *+l e ic7+ !as a 54 =C $ 1# a(*- a se e,pane aia/>(ica $ %eve%si/le*en(e 7as(a "na p%esi2n e #.4 a(*: / si la e,pansi2n es aia/>(ica c+n(%a "na p%esi2n c+ns(an(e e #.4 a(*. Calc"la% en l+s +s cas+s8 el v+l"*en inal- la (e*pe%a("%a inal- el (%a/aj+- el cal+%- la ene%!ía in(e%na $ la en(alpía. {a. 22$ '; #. 24$ '}
15.
Un !as *+n+a(2*ic+ ieal se lleva p+% el cicl+ %eve%si/le 6"e *"es(%a la + )atm* Calc@lese 9- ; $ U pa%a las (%a$ec(+%ias A- C $ CA. La (e*pe%a("%a el 5.0 es e 344 . Calc@lese 9- ; $ U pa%a el cicl+ (e%*+in>*ic+. )
∫ W = . 3 042 J }
C
2.0 A 10
16.
Un !as e,pe%i*en(a "n p%+ces+ cíclic+ 6"e c+*iena en el p"n(+ A: $ "n p%+ces+ A a v+l"*en c+ns(an(e- "n p%+ces+ C a p%esi2n c+ns(an(e p%+ces+ CA a (e*pe%a("%a c+ns(an(e. '>!ase 6"e el cicl+ sea lleva+ a 4.?# *+les e "n !as /ia(2*ic+ ieal- c+n PA 3.5 , 14# Pa-
*ic+. {
∫ W = 192 cal }
i!"%a. !as en A
30
( )l*
c+nsis(e en $ "n ca/+ s+/%e *3 $ P (a*/in-
+ )atm*
A
+,
+ 7
C ( )m3*
17.
Pa%a el c+/%e se (iene 4.#41 , 14 ) 1 $ k 4.?3# , 14 & a(* 1. Las capaciaes cal2%icas a p%esi2n $ v+l"*en c+ns(an(e- es(>n %elaci+naas así C P C< 5JkT<*. Calc"la% s(a ie%encia a (e*pe%a("%a $ p%esi2n a*/ien(e- $ e(e%*ine la ie%encia en cal+% necesa%i+ pa%a eleva% la (e*pe%a("%a e #44 !%a*+s e c+/%e 7as(a #4 a p%esi2n $ v+l"*en c+ns(an(e. La ensia el c+/%e es .? !Jc*3. {/+ − /( = 5.7410 J'; i!r!"cia ! calor = 2$7 J}
1$.
Un cilin%+ p%+vis(+ e "n pis(2n 6"e c+n(iene ai%e ve% i!"%a. El >%ea (%ansve%sal es e ) c*5 $ el v+l"*en inicial es e 54 c*3. El ai%e se enc"en(%a inicial*en(e a 1 a(* $ 54 +C. Al pis(2n se c+nec(a "n %es+%(e c"$a c+ns(an(e e e+%*aci2n es k s 144 NJc*- el c"al inicial*en(e n+ e,pe%i*en(a e+%*aci2n. KC">n(+ cal+% e/e aici+na%se al ai%e pa%a inc%e*en(a% la p%esi2n a 3 a(* Pa%a el ai%e c 4.1?1# ("Jl/*Q+. El apa%a(+ es(> %+ea+ e ai%e a(*+s%ic+. G0.0123 -t H
2
