Question

Part A

Predict the sign of the entropy change,
Part A Predict the sign of the entropy change,Delta S^circ, for each of thefollowing reactions.Part B Calculate the standard entropy change for the reaction using the data from the following table
, for each of thefollowing reactions.

1. $\rm Pb^{2+}{(aq)}+2Cl^-{(aq)}\rightarrow PbCl_2{(s)}$
2. $\rm CaCO_3{(s)}\rightarrow CaO{(s)}+CO_2{(g)}$
3. $\rm 2NH_3{(g)}\rightarrow N_2{(g)}+3H_2{(g)}$
4. $\rm P_4{(g)}+5O_2{(g)}\rightarrow P_4O_{10}{(s)}$
5. $\rm C_4H_8{(g)}+6O_2{(g)}\rightarrow 4CO_2{(g)}+4H_2O{(g)}$
6. $\rm I_2{(s)}\rightarrow I_2{(g)}$

Part B

Calculate the standard entropy change for the reaction

$\rm P_4{(g)}+5O_2{(g)}\rightarrow P_4O_{10}{(s)}$

using the data from the following table:

Substance	$\Delta H^\circ_{\rm f} ~{\rm (kJ/mol)}$	$\Delta G^\circ_{\rm f} ~{\rm (kJ/mol)}$	${S^\circ} ~{\rm [J/(K\cdot mol)]}$
$\rm P_4 {(g)}$	58.9	24.5	279.9
$\rm O_2{(g)}$	0	0	205.0
$\rm P_4O_{10} {(s)}$	2984	2698	228.9

Answer 1

Predict the sign of the entropy change, $\Delta S^\circ$ , for each of the following reactions.

1. $\rm Pb^{2+}{(aq)}+2Cl^-{(aq)}\rightarrow PbCl_2{(s)}$ ................negative......system isbecoming ordered into the solid state
2. $\rm CaCO_3{(s)}\rightarrow CaO{(s)}+CO_2{(g)}$ ...................positive.......a chaotic gas isproduced
3. $\rm 2NH_3{(g)}\rightarrow N_2{(g)}+3H_2{(g)}$ .......................positive.........2 gases to4 gases, more random and chaotic
4. $\rm P_4{(g)}+5O_2{(g)}\rightarrow P_4O_{10}{(s)}$ .....................negative..........system iscoelescing from chaotic gases to an ordered solid
5. $\rm C_4H_8{(g)}+6O_2{(g)}\rightarrow 4CO_2{(g)}+4H_2O{(g)}$ ........positive........6 gases to 8 gases, morerandom and chaotic
6. $\rm I_2{(s)}\rightarrow I_2{(g)}$ .................................................positive.........orderedsolid converting to chaotic gas

Answer 2

Calculate the standard entropy change for the reaction

$\rm P_4{(g)}+5O_2{(g)}\rightarrow P_4O_{10}{(s)}$

using the data from the following table:

Substance	$\Delta H^\circ_{\rm f} ~{\rm (kJ/mol)}$	$\Delta G^\circ_{\rm f} ~{\rm (kJ/mol)}$	${S^\circ} ~{\rm [J/(K\cdot mol)]}$
$\rm P_4 {(g)}$	58.9	24.5	279.9
$\rm O_2{(g)}$	0	0	205.0
$\rm P_4O_{10} {(s)}$	2984	2698	228.9

228.9 - 279.9 - 5(205.0) = result in J/K