Question

For the reaction `CO_((g))+(1)/(2)O_(2(g))rarrCO_(2(g)),DeltaH and DeltaS " are "-283 kJ and -87 JK^(-1)`. Respectively. It was intended to carry out this reaction at 1000, 1500, 3000 and 3500 K. At which of these temperature would this reaction be thermodynamically spontaneous
A. 1500 and 3500 K
B. 3000 and 3500 K
C. 1000, 1500 and 3000 K
D. 1500, 3000 and 3500 K

Answer 1

Correct Answer - C
`DeltaG=DeltaH-TDeltaS`
For spontaneous reaction `DeltaG` should be negative
When T=1000 K, `DeltaG`=(-283 -1000 `xx` 0.087) kJ =-370 kJ
When `T=1500 K, DeltaG=(-283-1500xx0.087) kJ =-413.5 kJ`
`T=3000 K, DeltaG=(-283-3000xx0.087) kJ=-544 kJ`
When `T=3500 K, DeltaG=(-283-3500xx0.087) kJ=+21.5 kJ`
Hence at 3500 K, reaction will be non-spontaneous.