Chemical Thermodynamics Question 283

Question: In order to decompose 9 g water 142.5 kJ heat is required.

Hence the enthalpy of formation of water is [KCET 2001]

Options:

A) - 142.5 kJ

B) + 142.5 kJ

C) - 285 kJ

D) + 285 kJ

Show Answer

Answer:

Correct Answer: C

Solution:

For the decomposition of 9gm of water heat required $ =142.5,kJ $ we know $ H_2O=2+16=18 $ Therefore heat required for decomposition of 18gm water $ =\frac{18}{9}\times 142.5=285,KJ $ Than, enthalpy of formation of water is reverse of heat required = - 285 kJ.



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