Verified Solution • 2025–26 Session moderate

QAIPM-2012-Ch-1691: NEET 2012 Chemistry - Class 11 AIPM-2012-Ch-1691 Solution: In which of the following reactions, standard reaction entropy…

In which of the following reactions, standard reaction entropy change (ΔS∘\Delta S^\circ) is positive and standard Gibb's energy change (ΔG∘\Delta G^\circ) decreases sharply with increasing temperature?

Multiple Choice Options

  • A C(graphite)+12O2(g)→CO(g)C(\text{graphite})+\frac{1}{2}O_2(g)\rightarrow CO(g)
  • B CO(g)+12O2(g)→CO2(g)CO(g)+\frac{1}{2}O_2(g)\rightarrow CO_2(g)
  • C Mg(s)+12O2(g)→MgO(g)Mg(s)+\frac{1}{2}O_2(g)\rightarrow MgO(g)
  • D 12C(graphite)+12O2(g)→12CO2(g)\frac{1}{2}C(\text{graphite})+\frac{1}{2}O_2(g)\rightarrow \frac{1}{2}CO_2(g)

Step-by-Step Verified Solution

_ S o positive means entropy of products is more than that of reactants. Among the given reactions only in option (a) the _ S o is positive cause products has 1 mole of gaseous products CO while reaction have half mole of gaseous O 2 and Carbon (C) in solid state. Thus, reactions have less randomness than products. Also, the reaction is a combustion reaction which has a negative value of _ H. According to Gibbs energy change ( _ S o ). _ G o = _ H o - T _ S o _ _ G o = -ve - T(+ve) Thus, on increasing temperature value of _ G o decreases sharply.

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