Why are hydrogen bonds considered a special class of dipole-dipole interactions?.

Ido not understand. 

Your question is not clear but if you can explain yourself i would be glad to .  just trying to : ))

Answerit curves up and levels out.explanationwe assume that the container contains absolutely no ammonia to begin with as it states that "nitrogen gas and hydrogen gas" react to "produce ammonia."at dynamic equilibrium, the product and reactant concentrations are equal.this means that, starting from a concentration of zero, [nh₃] must curve "up" from zero and then level out to a constant concentration.