HW #2: Cn 19 #'s 6,12,15,30,36,526,12,15,30,36,52
19-6) Ist law of TD tells us that the change in total internal energy of the system, Delta U=q+w\Delta U=q+w
or that a small change dU=delta q+delta wd U=\delta q+\delta w where q > 0q>0 : heat flows into the system
w>0: work done on the system
key to remember: *W\cdot W is minimiud when the prouss is reversible, omega_(min)=omega_("rev "){\omega_{m i n}}=\omega_{\text {rev }}
For reverside procoses, P_("ext ")~~P_("int ")=(nAT)/(V)P_{\text {ext }} \approx P_{\text {int }}=\frac{n A T}{V} so W_("evv ")=-int_(V_(1))^(V_(2))P_("ext ")dV=-int_(V_(1))^(V_(2))P_("int ")dV=-int_(V_(1))^(V_(2))(nAT)/(V)dVW_{\text {evv }}=-\int_{V_{1}}^{V_{2}} P_{\text {ext }} d V=-\int_{V_{1}}^{V_{2}} P_{\text {int }} d V=-\int_{V_{1}}^{V_{2}} \frac{n A T}{V} d V
Isotherm: constant TT W_("reV ")=-int_(V_(1))^(V_(2))P_("ext ")dV=-int_(V_(1))^(V_(2))P_("int ")dV=-int_(V_(1))^(V_(2))(nRT)/(V)dV=-nRTint_(V_(1))^(V_(2))(1)/(V)dV=-nRT ln V|_(V_(1))^(V_(2))=-nRT ln((V_(2))/(V_(1)))=nRT ln((V_(1))/(V_(2)))W_{\text {reV }}=-\int_{V_{1}}^{V_{2}} P_{\text {ext }} d V=-\int_{V_{1}}^{V_{2}} P_{\text {int }} d V=-\int_{V_{1}}^{V_{2}} \frac{n R T}{V} d V=-n R T \int_{V_{1}}^{V_{2}} \frac{1}{V} d V=-\left.n R T \ln V\right|_{V_{1}} ^{V_{2}}=-n R T \ln \left(\frac{V_{2}}{V_{1}}\right)=n R T \ln \left(\frac{V_{1}}{V_{2}}\right) n=5.00n=5.00 moles T=300kT=300 \mathrm{k} V_(1)=100.0dm^(3)quadV_(2)=40.0dm^(3)V_{1}=100.0 \mathrm{dm}^{3} \quad V_{2}=40.0 \mathrm{dm}^{3} w_("min ")=w_("rev ")=-n ATln((V_(1))/(V_(2)))=-5.00 cog((8.314(J))/(sin k))(300K)ubrace(ln[(40.0dmd^(8))/(100.00dm^(3))]ubrace)_(=ln(0.400))=+11,400J=11.4kJw_{\text {min }}=w_{\text {rev }}=-n \operatorname{ATln}\left(\frac{V_{1}}{V_{2}}\right)=-5.00 \operatorname{cog}\left(\frac{8.314 \mathrm{~J}}{\sin k}\right)(300 \mathrm{~K}) \underbrace{\ln \left[\frac{40.0 \mathrm{dm} \mathrm{d}^{8}}{100.00 \mathrm{dm}^{3}}\right]}_{=\ln (0.400)}=+11,400 \mathrm{~J}=11.4 \mathrm{~kJ}
Where there this comes from:
Our general desinition of Work is W=F*Deltah^(')W=F \cdot \Delta h^{\prime}, where WW has units of N*m=JN \cdot m=J, which are units of energy
use det P=(F)/(A)=>F=PA=>W=Pubrace(A*Delta hubrace)_(Delta V)=P Delta VP=\frac{F}{A} \Rightarrow F=P A \Rightarrow W=P \underbrace{A \cdot \Delta h}_{\Delta V}=P \Delta V
Explain neg.sign: define w > 0w>0 as work done on gas
Compression: V_(2) < V_(1)-int_(V_(1))^(V_(2))P_("ext ")dV=-P_("ext ")(ubrace(V_(2)-V_(1)ubrace)_((-)))=-(-)P_("ext ")Delta V=P_("ext ")Delta V,quad uarr Delta UV_{2}<V_{1}-\int_{V_{1}}^{V_{2}} P_{\text {ext }} d V=-P_{\text {ext }}(\underbrace{V_{2}-V_{1}}_{(-)})=-(-) P_{\text {ext }} \Delta V=P_{\text {ext }} \Delta V, \quad \uparrow \Delta U, work done on gas
Expansion: V_(2) > V_(1)-int_(V_(1))^(V_(2))p_("ext ")dV=-p_("ext ")(ubrace(V_(2)-V_(1)ubrace)_((+)))=-p_("ext ")Delta VV_{2}>V_{1}-\int_{V_{1}}^{V_{2}} p_{\text {ext }} d V=-p_{\text {ext }}(\underbrace{V_{2}-V_{1}}_{(+)})=-p_{\text {ext }} \Delta V, darr Delta U\downarrow \Delta U, gus does work
19-12) quadP_(1)=2.00barquadP_(2)=4.00barquad(P)/(V)=C=\quad P_{1}=2.00 \mathrm{bar} \quad P_{2}=4.00 \mathrm{bar} \quad \frac{P}{V}=C= constant * qq and ww are not state frns. Ther values are path-dependent
{:[T_(1)=273k,T_(2)=?,=>P=VC],[V_(1)=?,V_(2)=?, bar(C)_(V)=12.5((J))/((mol)*(h))]:}quad" * reversibu, so "w=-int_(V_(1))^(V_(2))P_("ext ")dV=-int_(V_(1))^(V_(2))P_("int ")dV", can use ideal ges law "\begin{array}{lll}
T_{1}=273 \mathrm{k} & T_{2}=? & \Rightarrow P=V C \\
V_{1}=? & V_{2}=? & \bar{C}_{V}=12.5 \frac{\mathrm{~J}}{\mathrm{~mol} \cdot \mathrm{~h}}
\end{array} \quad \text { * reversibu, so } w=-\int_{V_{1}}^{V_{2}} P_{\text {ext }} d V=-\int_{V_{1}}^{V_{2}} P_{\text {int }} d V \text {, can use ideal ges law }
Using ideal gas law, can find V_(1),V_(2),T_(2)V_{1}, V_{2}, T_{2}, and CC : quad PV=nRT\quad P V=n R T
Delta U=q+w=>q=Delta U-w=10.2kJ-(-3.40kJ)=13.6kJ\Delta U=q+w \Rightarrow q=\Delta U-w=10.2 \mathrm{~kJ}-(-3.40 \mathrm{~kJ})=13.6 \mathrm{~kJ}
Enthalpy is a quantity we define as: H=U+ubrace(ubrace)_(se+PV)=H=U+\underbrace{}_{s e+P V}= RAT Delta H=Delta U+P Delta V+V Delta P=ubrace(Delta U+" nRAT "ubrace)_(T_("easher to compute "))\Delta H=\Delta U+P \Delta V+V \Delta P=\underbrace{\Delta U+\text { nRAT }}_{T_{\text {easher to compute }}}
so Delta H=Delta U+\Delta H=\Delta U+ nR Delta T=10.2kJ+ubrace(1.00mot(8.31(4(J))/(K*908))(1092(K)-273(K))ubrace)_(6,809.23=6.8kJ)=(10.2+6.8)kJ=17.0kJ\Delta T=10.2 \mathrm{~kJ}+\underbrace{1.00 \mathrm{mot}\left(8.31 \frac{4 \mathrm{~J}}{K \cdot 908}\right)(1092 \mathrm{~K}-273 \mathrm{~K})}_{6,809.23=6.8 \mathrm{~kJ}}=(10.2+6.8) \mathrm{kJ}=17.0 \mathrm{~kJ}
19-15) Show (T_(2))/(T_(1))=((V)/(V_(2)))^((Lambda)/( bar(C_(v))))\frac{T_{2}}{T_{1}}=\left(\frac{V}{V_{2}}\right)^{\frac{\Lambda}{\overline{C_{v}}}} for reversible adiabatic expansion of ideal gas
adiabatic: delta_(q)=0\delta_{q}=0 dU=deltaxi^(0)+delta w=delta w quad=>dU=delta wd U=\delta \xi^{0}+\delta w=\delta w \quad \Rightarrow d U=\delta w
*want to rewrite dUd U and delta w\delta w, then work out a relationship:
We can write U (or any state function) as a total disserential: U(T,V)=>dU=(del U)/(del T))_(V)dT+(del U)/(del V)|_(T)dV quad\left.U(T, V) \Rightarrow d U=\frac{\partial U}{\partial T}\right)_{V} d T+\left.\frac{\partial U}{\partial V}\right|_{T} d V \quad Use: dU=n bar(C)_(V)dT quadd U=n \bar{C}_{V} d T \quad Q quadw_("reV ")=-int_(P_("ext "))dV=-int_("int ")dV=-int(nRT)/(V)dV\quad w_{\text {reV }}=-\int_{P_{\text {ext }}} d V=-\int_{\text {int }} d V=-\int \frac{n R T}{V} d V (del U)/(del N))_(T)=0\left.\frac{\partial U}{\partial N}\right)_{T}=0 for ideal gas rarr\rightarrow asour Uonly changs w//T: bar(U)=(3)/(2)RTw / T: \bar{U}=\frac{3}{2} R T
(each D.O.F contriburs (RT)/(2)\frac{R T}{2} to bar(U)\bar{U} ) {:[=>dU=deltaomega_("reV "),quadP_("ext ")=P_("int for ")" revesible work "],[n bar(C)_(V)dT=-P_("int ")d bar(V)," sub "P=(nRT)/(V)]:}\begin{array}{ll}\Rightarrow d U=\delta \omega_{\text {reV }} & \quad P_{\text {ext }}=P_{\text {int for }} \text { revesible work } \\ n \bar{C}_{V} d T=-P_{\text {int }} d \bar{V} & \text { sub } P=\frac{n R T}{V}\end{array} A bar(C)dT=(-QRT)/(V)dVA \bar{C} d T=\frac{-Q R T}{V} d V reacrange int_(T_(1))^(T_(2))( bar(C_(V))dT)/(T)=int_(V_(1))^(V_(2))(-R)/(V)dV\int_{T_{1}}^{T_{2}} \frac{\overline{C_{V}} d T}{T}=\int_{V_{1}}^{V_{2}} \frac{-R}{V} d V Integrate B.S. bar(C_(V))ln T|_(T_(1))^(T_(2))=-R ln V|_(V_(1))^(V_(2))\left.\overline{C_{V}} \ln T\right|_{T_{1}} ^{T_{2}}=-\left.R \ln V\right|_{V_{1}} ^{V_{2}} bar(C_(v)ln((T_(2))/(T_(1))))=- widehat(R ln((V_(2))/(V_(1))))\overline{C_{v} \ln \left(\frac{T_{2}}{T_{1}}\right)}=-\widehat{R \ln \left(\frac{V_{2}}{V_{1}}\right)} e^(ln ((T_(2))/(T_(1)))^( bar(V_(v)))=e^(ln ((V_(2))/(V_(1)))^(-R))quad" exponentiate B.S. ")e^{\ln \left(\frac{T_{2}}{T_{1}}\right)^{\overline{V_{v}}}=e^{\ln \left(\frac{V_{2}}{V_{1}}\right)^{-R}} \quad \text { exponentiate B.S. }}
{:[(((T_(2))/(T_(1)))^(( bar(S_(1)))/(V_(1))))^((1)/(V_(1)))=(((V_(2))/(V_(1)))^(-R))^((1)/(V_(v)))quad" raise B.S. to "((1)/(C_(v)))],[((T_(2))/(T_(1)))=((V_(2))/(V_(1)))^((-1)/(C_(v)))=((V_(1))/(V_(2)))^((h)/(C_(v)))//]:}\begin{aligned}
& \left(\left(\frac{T_{2}}{T_{1}}\right)^{\frac{\overline{S_{1}}}{V_{1}}}\right)^{\frac{1}{V_{1}}}=\left(\left(\frac{V_{2}}{V_{1}}\right)^{-R}\right)^{\frac{1}{V_{v}}} \quad \text { raise B.S. to }\left(\frac{1}{C_{v}}\right) \\
& \left(\frac{T_{2}}{T_{1}}\right)=\left(\frac{V_{2}}{V_{1}}\right)^{\frac{-1}{C_{v}}}=\left(\frac{V_{1}}{V_{2}}\right)^{\frac{h}{C_{v}}} /
\end{aligned}
sin u((V_(2))/(V_(1)))^(-1)=(V_(1))/(V_(2))\sin u\left(\frac{V_{2}}{V_{1}}\right)^{-1}=\frac{V_{1}}{V_{2}}
19-30) Fur ideal gas: ((del U)/(del V))_(T)=0\left(\frac{\partial U}{\partial V}\right)_{T}=0, prove ((del H)/(del V))_(T)=0\left(\frac{\partial H}{\partial V}\right)_{T}=0
Recall H=U+PV=^(" ideal gas law ")U+nRTH=U+P V \stackrel{\text { ideal gas law }}{=} U+n R T
If keep H=U+PVH=U+P V, need to use product rule on ((del)/(del V)(PV))_(T)\left(\frac{\partial}{\partial V}(P V)\right)_{T} :
{:[((del H)/(del V))_(T)=((del V)/(del V))_(T)^(0)+ubrace((nR)/((del nRT)/(del V)))_(T)ubrace)=0],[" since "T" is constant! "]:}\begin{gathered}
\left(\frac{\partial H}{\partial V}\right)_{T}=\left(\frac{\partial V}{\partial V}\right)_{T}^{0}+\underbrace{\left.\frac{n R}{\frac{\partial n R T}{\partial V}}\right)_{T}}=0 \\
\text { since } T \text { is constant! }
\end{gathered}
{:[((del H)/(del V))_(T)=((del U)/(del V))_(T)^(T^(0))+V((del P)/(del V))_(T)+P(ubrace((del V)/(del V)ubrace)_(=1))_(T)],[((del H)/(del V))_(T)=V((del P)/(del V))_(T)+P larr" sub "P=(nRT)/(V)],[((del H)/(del V))_(T)=V((del)/(del V)(nRT)/(V))_(T)+(nRT)/(V)=X((-nRT)/(V^(2)))+(nRT)/(V)=(-nRT)/(V)+(nRT)/(V)=0]:}\begin{aligned}
& \left(\frac{\partial H}{\partial V}\right)_{T}=\left(\frac{\partial U}{\partial V}\right)_{T}^{T^{0}}+V\left(\frac{\partial P}{\partial V}\right)_{T}+P(\underbrace{\frac{\partial V}{\partial V}}_{=1})_{T} \\
& \left(\frac{\partial H}{\partial V}\right)_{T}=V\left(\frac{\partial P}{\partial V}\right)_{T}+P \leftarrow \text { sub } P=\frac{n R T}{V} \\
& \left(\frac{\partial H}{\partial V}\right)_{T}=V\left(\frac{\partial}{\partial V} \frac{n R T}{V}\right)_{T}+\frac{n R T}{V}=X\left(\frac{-n R T}{V^{2}}\right)+\frac{n R T}{V}=\frac{-n R T}{V}+\frac{n R T}{V}=0
\end{aligned}
19-52) {:[omega=ubrace(P_(1)V_(1)-P_(2)V_(2)ubrace)quad" (given) "],[" Ist law TD: "q=0" since no neat exchange w/ environment "],[Delta v=U_(2)-U_(1)=lambda^(0)+omega^(2)]:}\begin{aligned} \omega & =\underbrace{P_{1} V_{1}-P_{2} V_{2}} \quad \text { (given) } \\ \text { Ist law TD: } & q=0 \text { since no neat exchange w/ environment } \\ \Delta v & =U_{2}-U_{1}=\lambda^{0}+\omega^{2}\end{aligned}
rearlang: quadubrace(V_(2)+P_(2)V_(2)ubrace)_(H_(2))=ubrace(V_(1)+P_(1)V_(1)ubrace)_(H_(1))=>{:[Delta H=H_(2)-H_(1)=O],[" since "H_(2)=H_(1)]:}\quad \underbrace{V_{2}+P_{2} V_{2}}_{H_{2}}=\underbrace{V_{1}+P_{1} V_{1}}_{H_{1}} \Rightarrow \begin{aligned} & \Delta H=H_{2}-H_{1}=O \\ & \text { since } H_{2}=H_{1}\end{aligned}
Total elevivotive of HH as function of P,T:H(P,T)P, T: H(P, T)
{:[dH=((del H)/(del P))_(T)dP+((del H)/(del T))_(P)dT quad" Apply: "((del H)/(del T))_(P)=C_(P)quad**" Recall "dH=0],[dT=(-1)/(C_(P))((del H)/(del P))_(T)dP],[dH=((del H)/(del P))_(T)dP+C_(P)dT],[-C_(PdT)=((dH)/(del P))_(T)dP-dH],[" This is a total differential, but because this is a special case of "dH=0],[(" constant "H)", can rewrite: "quad((del T)/(del P))_(H)=(-1)/(C_(P))((del H)/(del P))_(T)],[dT=-(1)/(C_(P))((del H)/(del P))_(T)dP+(1)/(C_(P))dH],[mu_(ST)=((del T)/(del P))_(H){:[" is called the Joules-Thonson coefsicient. It measures "],[" the change in temperature with respect to a change in "]:}],[" pressure in a Jolles-Thomson expansion. "Delta H=0" for "],[" Joules-Thomson expansions "]:}\begin{aligned}
& d H=\left(\frac{\partial H}{\partial P}\right)_{T} d P+\left(\frac{\partial H}{\partial T}\right)_{P} d T \quad \text { Apply: }\left(\frac{\partial H}{\partial T}\right)_{P}=C_{P} \quad * \text { Recall } d H=0 \\
& d T=\frac{-1}{C_{P}}\left(\frac{\partial H}{\partial P}\right)_{T} d P \\
& d H=\left(\frac{\partial H}{\partial P}\right)_{T} d P+C_{P} d T \\
& -C_{P d T}=\left(\frac{d H}{\partial P}\right)_{T} d P-d H \\
& \text { This is a total differential, but because this is a special case of } d H=0 \\
& (\text { constant } H) \text {, can rewrite: } \quad\left(\frac{\partial T}{\partial P}\right)_{H}=\frac{-1}{C_{P}}\left(\frac{\partial H}{\partial P}\right)_{T} \\
& d T=-\frac{1}{C_{P}}\left(\frac{\partial H}{\partial P}\right)_{T} d P+\frac{1}{C_{P}} d H \\
& \mu_{S T}=\left(\frac{\partial T}{\partial P}\right)_{H} \begin{array}{l}
\text { is called the Joules-Thonson coefsicient. It measures } \\
\text { the change in temperature with respect to a change in }
\end{array} \\
& \text { pressure in a Jolles-Thomson expansion. } \Delta H=0 \text { for } \\
& \text { Joules-Thomson expansions }
\end{aligned}