$3\mathrm{.}6$ If the gas has an initial pressure of $20\mathrm{.}27$ bar in a reversible isothermal expansion of an ideal gas of $300K$ from $1L$ to $10$ L$,$ calculate $($a$)$ the $4S$ of the gas and $($b$)$ the AS for the entire system contained in the expansion.

$3\mathrm{.}71$ body oxygen expands reversibly from I bar to $0\mathrm{.}1$ bar at $298K.$ The change in entropy of the gas is $7,$ and what is the change in entropy for the gas plus the heat source contacted by the gas?

$[3\mathrm{.}4.$ Verse$]$

$3\mathrm{.}8$ An ideal gas of $3\mathrm{.}8$ undergoes an isothermal reversible expansion at $300K$ from $90L$ to $300L.($a$)$ Calculate AU$,$ AS$,$ w and q for this system. $($b$)$ Calculate AU$,$ AS$,$ W per mole and $4$ per mole. $($c$)$ If the expansion proceeded irreversibly by allowing the gas to expand into the vacuum container, what are the values of AU$.$ AS$.$ W per mole and $93$ per mole?

$3\mathrm{.}9($a$)$ A system consists of one mole of ideal gas that performs the following state changes.

$1x(g.298K,10$ bar $)1(g.298K,1$ bar$)$

If the expansion is reversible, what is the value of AS$?$ If the gas expands to a large vacuum container and the final pressure is $1$ bar, what is the value of $4S?($b$)$ The same state change occurs, but let's think that adding gas to the heat source at $298K$ makes it our system now. What is the value of AS in a reversible expansion? If the gas expands to a larger container and the final pressure is I bar, what is the value of AS$?$

$3\mathrm{.}10$ An ideal gas of $298K$ undergoes isothermal expansion at a pressure of $10$ bar to $\frac{1}{b}ar.($a$)$ reversible expansion, $($b$)$ free Pyeongchang, $($c$)$ when the gas and its surroundings form a single isolated system and undergo reversible expansion. $($d$)$ when the gas and its surroundings form a single isolated system and expand freely, what are the values of W$.$ AU AH and AS per mole?

$3\mathrm{.}11$ The monoatomic ideal gas was heated from $300K$ to $1000K,$ and the pressure was added from $1$ bar to $2$ bar. What is the molar entropy change?

$3\mathrm{.}12$ The purest acetic acid is called glacial acetic acid because it is purified by fractional freezing at $16\mathrm{.}6C,$ the melting point. At $16\mathrm{.}6C,$ a flask containing several moles of acetic acid was immersed in an ice$-$water bath for a while. When I took out this flask, I found that exactly one mole of acetic acid was frozen.

When AfusH $(CH3$COH$)=11\mathrm{.}45kJ$ mol $\text{'}$ and AfusH$($H$2$O$)=5\mathrm{.}98kJ$ mol $1.($a$)$ What is the change in entropy of acetic acid? $($b$)$ What is the change in entropy of the water tank? $($c$)$ Now consider that the water tank is the same system as acetic acid. What is the change in entropy of a combined system? Is this process reversible or irreversible? Why?

$[$Verse $3\mathrm{.}5]$

$3\mathrm{.}13$ In Exercise $2\mathrm{.}23$ the final pressure of $1$ mole of a monoatomic ideal gas of $\frac{1}{b}ar$ and $300K$ is $1$

$2$ bar, until temperature

reaches $240KI$

There is a single expansion for a constant pressure of $2$ bar. What is the value of AS for this process?

$3\mathrm{.}1410$ moles of $H2$ and $22$ moles of $D$ were mixed at $25C$ and $1$ bar. Assuming that it is an ideal gas, what is the value of $AS?$

$3\mathrm{.}15($a$)$ Use yi to describe the equation for the entropy of an ideal gas A$.$ B$.$ C mixture at T and P$.($b$)$ Now let's try two steps to combine the terms that contribute to the entropy of the system. First, imagine that gases A and $C$ are mixed to form mixtures with moles of $r$ and $r$ in which moles in the mixtures A and $C$ are formed, but $B$ is not mixed. Write down the equation for the entropy of a system having two terms, $i=nA+nc,$ and the term $"$BS B$",$ which contributes to the pressure $P1=Pa+Pc.$