Chapter 9, Problem 9.73PAE

9.73 Without looking up any numerical data or doing calculations, predict whether the enthalpy change for each of the following reactions should he positive, negative, or zero.

(a) ${\text{H}}_{\text{2}}\text{O}\left(\mathcal{l}\right){\text{H}}_{\text{2}}\text{O(s)}$

(b) ${\text{N}}_{\text{2}}\left(\text{g}\right)\to 2\text{N}\left(\text{g}\right)$

(c) ${\text{CH}}_{\text{4}}\left(\text{g}\right)+{\text{2O}}_{\text{2}}\left(\text{g}\right)\to {\text{CO}}_{\text{2}}\left(\text{g}\right)+{\text{2H}}_{\text{2}}\text{O}\left(\mathcal{l}\right)$

(d) ${\text{CO}}_{\text{2}}\left(\text{s}\right)\to {\text{CO}}_{\text{2}}\left(\text{g}\right)$