Question 20

[admin]

Note that paragraph 2 states:

With cold, dilute alkali at 15 oC, all of the halogens, except fluorine, react to yield a mixture of halide (Hal-) and hypohalite (HalO-) as shown in Reaction I.

Then paragraph 3 states:

The hypohalite then decomposes to yield halide and halate (HalO3-). This reaction is shifted to the right on the application of heat.

The first sentence in paragraph 3 (above) clearly describes Reaction II (not Reaction I). The second sectence means that we can rewrite Reaction II as follows:

3HalO- + heat <--> 2Hal- + HalO3-

Thus Reaction II is endothermic = positive enthalpy.