An engineer is designing a process to cool hot water from a power plant before returning the water to the environment. his plan is to allow the hot water to flow past a pipe containing a solution that is undergoing a chemical reaction. the chemical reaction will be able to remove some of the water's heat through the metal pipe. which of the following reactions could take place inside the cooling pipe to remove heat from the hot water? a. c + o2 → co2 + heat b. cacl2 → ca2+ + 2cl- + heat c. nh4cl + heat → nh4+ + cl- d. n2 + 3h2 → 2nh3 + heat

Analysis of the set of options:

A. C + O2 → CO2 + heat

The heat on the right side means that the reaction release (yields) heat. This is an exothermic reaction. Relasing heat means that the surrondings will receive an extra amount of heat as consequence of the reaction, so this reaction is not suitable to the target of cooling hot water.

This is a wrong choice.

B. CaCl2 → Ca2+ + 2Cl- + heat

This is the same situation explained above. An exothermic reaction which will increase the temperature of the water instead  of cooling it.

Wrong choice.

C. NH4Cl + heat → NH4+ + Cl-

This is the right choice.

The heat shown in the side of the reactants means that the reaction uses (absorbs) heat. Where from will the reaction absorb this heat? From the surroundings which include the hot water. In conclusion, the reaction will use heat from the hot water consequently cooling it.

D. N2 + 3H2 → 2NH3 + heat

The very same case of the first two options. Wrong choice, because it iis an exothermic reaction which will increase the temperature of the surroundings.