why do you think that scientist add excess of one or more chemicals when performing a reaction rather than combine the exact stoichionetric ratio

Copper, silver, aluminum, cobalt, chromium, mercury 

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.

The higher the temperature, the increased rate constant for a reaction.(positive linear association)