Question

For a reaction, AH = 176 kJ/mol and A SO = 0.285 kJ/(K•mol). At what

temperatures is this reaction spontaneous?
A. At no temperature
B. T< 50 K
C. T>617 K
D. T< 617 K

Answer 1

C. T>617 K

Step-by-step explanation:

We are given that

`\Delta H=176KJ/mol`

`\Delta S=0.285KJ/K\cdot mol`

We have to find the temperature at which the reaction is spontaneous.

When

`\Delta H>0, \Delta S>0`

Therefore, the reaction is spontaneous at certain range of temperature.

Option A is not true.

`\Delta G=\Delta H-T\Delta S`

When
`\Delta G` is negative, then the reaction is spontaneous.

`\Delta G=176-0.285T`

When T<50

Suppose T=49 K

`\Delta G=176-49* 0.285>0`

Therefore,
`\Delta G is positive`.Hence, the reaction is not spontaneous.

Option B is wrong.

C.T>617K

Suppose T=618 K

`\Delta G=176-0.285* 618=-0.13<0`

Therefore,
`\Delta G is negative`.Hence, the reaction is spontaneous.

So, option C is true.

D.T<617 K

Suppose T=616 K

`\Delta G=176-0.285* 616=0.44>0`

Therefore,
`\Delta G is positive`.Hence, the reaction is not spontaneous.

So, option D is not true.