Entropy for a Reversible Process

Q. The equilibrium constant for the reaction given below is $2.0\times {10}^{-7}$ at 300 K. Calculate the standard entropy change if $△H^{\circ }=28.40kJmo{l}^{-1}$ for the reaction:
$PC{l}_5\left(g\right)\rightleftharpoons PC{l}_3\left(g\right)+C{l}_2\left(g\right)$

1. $-33.6Jmo{l}^{-1}{K}^{-1}$
2. $33.6Jmo{l}^{-1}{K}^{-1}$
3. $-43.6Jmo{l}^{-1}{K}^{-1}$
4. $43.6Jmo{l}^{-1}{K}^{-1}$

Q. 1 mole of an ideal gas at ${25}^{\circ }C$ is subjected to expand reversibly 10 times of its initial volume. Calculate the change in entropy of expansions.

1. 25.15 $J{K}^{-1}mo{l}^{-1}$
2. 30.15 $J{K}^{-1}mo{l}^{-1}$
3. 19.15 $J{K}^{-1}mo{l}^{-1}$
4. 29.15 $J{K}^{-1}mo{l}^{-1}$

Q. 1 mole of an ideal gas at 20 atm pressure and 15 L volume expands such that the final pressure becomes 10 atm and the final volume becomes 60 L. Calculate the change in entropy for the process.
$(C_{p.m}=30{\text{J mole}}^{-1}{\text{K}}^{-1},R=\frac{25}{3}\text{J/mol K, ln 2 = 0.7, ln 3 = 1.1})$.

1. $80.2{\text{JK}}^{-1}{\text{mole}}^{-1}$
2. $15.17{\text{JK}}^{-1}{\text{mol}}^{-1}$
3. $120\times {10}^2{\text{JK}}^{-1}{\text{mol}}^{-1}$
4. $26.83{\text{JK}}^{-1}{\text{mol}}^{-1}$

Q. Acetic acid forms a dimer in the gas phase
The dimer is held together by two hydrogen bonds with a total strength of 66.5 kJ per mole of dimer. At ${25}^{o}C,$ the equilibrium constant for the dimerisation is $1.3\times {10}^3$ (pressure in atm). What is magnitude $△S^0$ for the reaction? Assume that $△H$ does not vary with temperature.

Q. Acetic acid $C{H}_{3}COOH$ can form a dimer $(C{H}_{3}COOH{)}_2$ in the gas phase. The dimer is held together by two H - bonds with a total strength of $77.43kJpermol$ of dimer.
If at ${27}^{\circ }C$, the equilibrium constant for the dimerization is $1.096\times {10}^3$, then calculate the magnitude of $\Delta S^{\circ }$ (in $kJ$) for the reaction:
$2C{H}_{3}COOH\left(g\right)\rightleftharpoons \left(C{H}_{3}COOH{)}_2\right(g)$ (Round upto 2 digits after decimal and $\ln \left(1.096\times {10}^3\right)\approx 7andR=8.3J{K}^{-1}mo{l}^{-1}$)

Q.

For the homogeneous gas phase equilibrium $4N{H}_3\left(g\right)+5O_2\left(g\right)\iff 4NO\left(g\right)+6H_{2}O\left(g\right)$ the units of equilibrium constant ${}^{\prime }{K}_C^{\prime }$ are

1. mol L${}^{-1}$

2. L mol${}^{-1}$

3. mol${}^2$ L${}^2$

4. L${}^2$ mol${}^{-2}$

Q. Calculate the entropy$(J{K}^{-1}$ mol${}^{-1})$ change for the following reversible process:
$\alpha -Tin\rightleftharpoons \beta -Tin$ at ${13}^{\circ }C$
1 mol at 1 atm
$\Delta H_{\text{trans}}=2288J$ mol${}^{-1}$

1. 8
2. 10
3. 5
4. \N

Q. A sample of an ideal gas is expanded to twice its original volume of $1m^3$ in a reversible process for which $P=\alpha v^2$ where α=5 $atm/m^6$ . If $C_{v,m}=20Jmo{l}^{-1}{K}^{-1}$, determine the approximate molar change in entropy for the process.

1. $4Jmo{l}^{-1}{K}^{-1}$
2. $47.35Jmo{l}^{-1}{K}^{-1}$
3. $40Jmo{l}^{-1}{K}^{-1}$
4. $4Jmo{l}^{-1}{K}^{-1}$

Q.

For the homogeneous gas phase equilibrium $4N{H}_3\left(g\right)+5O_2\left(g\right)\iff 4NO\left(g\right)+6H_{2}O\left(g\right)$ the units of equilibrium constant ${}^{\prime }{K}_C^{\prime }$ are

1. mol L${}^{-1}$

2. L mol${}^{-1}$

3. mol${}^2$ L${}^2$

4. L${}^2$ mol${}^{-2}$