The following reaction is spontaneous at all temperatures: CaC 2 ( s ) + 2H 2 O(

Question

The following reaction is spontaneous at all temperatures:

CaC2(s) + 2H2O(l) ? Ca(OH)2(s) + C2H2(g)

Which of the following statements is true?

?H is positive and ?S is negative.

?H is positive and ?S is positive.

?H is negative and ?S is positive.

?H is negative and ?S is negative.

?G is positive at all temperatures.

?H is positive and ?S is negative.

?H is positive and ?S is positive.

?H is negative and ?S is positive.

?H is negative and ?S is negative.

?G is positive at all temperatures.

Explanation / Answer

delta G = delta H - T* delta S.

Now, Since n(gas) > 0 for reaction. delta S is positive.

Now for spontaneous reaction,

deLta G < 0

or, delta H - T * delta S < 0

or, delta H < T * delta S.

Hence, T is always positive.

So, delta H can be negative and delta S is positive.

So, delta H can be positive and delta S also.

So, delta H cant be positive when delta S is negative.

Hence,

b) , c)

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