If for a certain reaction ΔrH is 30 kJ mol-1 at 450 K, the value of ΔrS (in JK-1 mol-1) for which the same reaction will be spontaneous at the same temperature is

Question

If for a certain reaction ΔrH is 30 kJ mol-1 at 450 K, the value of ΔrS (in JK-1 mol-1) for which the same reaction will be spontaneous at the same temperature is (A) 70 (B) -33 (C) 33 (D) -70

Tardigrade Admin · Accepted Answer

Δ G=Δ H-T Δ S For spontaneous, Δ G < 0 Δ H-T Δ S< O Δ S> (Δ H/T) Δ S > (30 × 103 J mol-1/450 K) Δ S> 66.6 J mol-1 K-1 (Check by options)

Q. If for a certain reaction $Δ_{r} H$ is $30 k J m o l^{- 1}$ at $450 K$ , the value of $Δ_{r} S$ (in $J K^{- 1} m o l^{- 1})$ for which the same reaction will be spontaneous at the same temperature is

$70$

$- 33$

$33$

$- 70$

$Δ G = Δ H - T Δ S$
For spontaneous,
$Δ G < 0$
$Δ H - T Δ S < O$
$Δ S > \frac{Δ H}{T}$
$Δ S > \frac{30 \times 1 0 ^{3} J m o l ^{- 1}}{450 K}$
$Δ S > 66.6 J m o l^{- 1} K^{- 1}$ (Check by options)

Q. If for a certain reaction Δr​H is 30kJmol−1 at 450K, the value of Δr​S (in JK−1mol−1) for which the same reaction will be spontaneous at the same temperature is

70

−33

33

−70