*i think it’s either the first one or the last one, but i’m just not sure. nitrogen dioxide gas is dark brown in color and remains in equilibrium with dinitrogen tetroxide gas, which is colorless. 2no2(g) ⇌ n2o4(g) when the light brown color equilibrium mixture was moved from room temperature to a lower temperature, the mixture turned lighter brown in color. which of the following conclusions about this equilibrium mixture is true? this reaction is endothermic because the system shifted to the left on cooling. this reaction is endothermic because the system shifted to the right on cooling. this reaction is exothermic because the system shifted to the left on cooling. this reaction is exothermic because the system shifted to the right on cooling.

This reaction is exothermic because the system shifted to the right on cooling.  

Step-by-step explanation:

 2NO₂   ⇌   N₂O₄

brown    colourless

According to Le Châtelier's Principle, when a stress is applied to a system at equilibrium, the system will respond in a way that tends to relieve the stress.

You applied a stress by cooling the system (removing heat). The system responded by moving in a direction that created more heat.

The mixture became lighter brown on cooling, so the position of equilibrium must have shifted to the right to generate the heat.

The reaction is exothermic.

chemical changes occur when a substance combines with another to form a new substance, called chemical synthesis or, alternatively, chemical decomposition into two or more different substances. these processes are called chemical reactions and, in general, are not reversible except by further chemical reactions. some reactions produce heat and are called exothermic reactions and others may require heat to enable the reaction to occur, which are called endothermic reactions. understanding chemical changes is a major part of the science of chemistry.