Question

In an irreversible process taking place at constant $$T$$ and $$P$$ and in which only pressure-volume work is being done, the change in Gibbs free energy $$(dG)$$ and change in entropy $$(dS),$$ satisfy the criteria

A. $${\left( {dS} \right)_{V.E}} > 0,{\left( {dG} \right)_{T.P}} < 0$$  
B. $${\left( {dS} \right)_{V.E}} = 0,{\left( {dG} \right)_{T.P}} = 0$$
C. $${\left( {dS} \right)_{V,E}} = 0,{\left( {dG} \right)_{T.P}} > 0$$
D. $${\left( {dS} \right)_{V,E}} < 0,{\left( {dG} \right)_{T.P}} < 0$$
Answer :   $${\left( {dS} \right)_{V.E}} > 0,{\left( {dG} \right)_{T.P}} < 0$$
Solution :
For spontaneous reaction, $$dS > 0$$  and $$dG$$ should be negative ie. $$<0.$$

Releted MCQ Question on
Physical Chemistry >> Chemical Thermodynamics

Releted Question 1

The difference between heats of reaction at constant pressure and constant volume for the reaction : $$2{C_6}{H_6}\left( l \right) + 15{O_{2\left( g \right)}} \to $$     $$12C{O_2}\left( g \right) + 6{H_2}O\left( l \right)$$     at $${25^ \circ }C$$  in $$kJ$$ is

A. $$-$$ 7.43
B. $$+$$ 3.72
C. $$-$$ 3.72
D. $$+$$ 7.43
Releted Question 2

For which change $$\Delta H \ne \Delta E\,:$$

A. $${H_{2\left( g \right)}} + {I_{2\left( g \right)}} \to 2HI\left( g \right)$$
B. $$HC{\text{l}} + NaOH \to NaC{\text{l}}$$
C. $${C_{\left( s \right)}} + {O_{{2_{\left( g \right)}}}} \to C{o_{{2_{\left( g \right)}}}}$$
D. $${N_2}\left( g \right) + 3{H_2}\left( g \right) \to 2N{H_3}\left( g \right)$$
Releted Question 3

$${\text{The}}\,\Delta H_f^0\,{\text{for}}\,C{O_2}\left( g \right),\,CO\left( g \right)\,$$     and $${H_2}O\left( g \right)$$   are $$-393.5,$$  $$-110.5$$  and $$ - 241.8\,kJ\,mo{l^{ - 1}}$$    respectively. The standard enthalpy change ( in $$kJ$$ ) for the reaction $$C{O_2}\left( g \right) + {H_2}\left( g \right) \to CO\left( g \right) + {H_2}O\left( g \right)\,{\text{is}}$$

A. 524.1
B. 41.2
C. -262.5
D. -41.2
Releted Question 4

In thermodynamics, a process is called reversible when

A. surroundings and system change into each other.
B. there is no boundary between system and surroundings.
C. the surroundings are always in equilibrium with the system.
D. the system changes into the surroundings spontaneously.

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Chemical Thermodynamics


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