The reaction N2O4 (g) <--> 2NO2 (g) is endothermic, meaning that it consumes heat to move towards formation of the products.
According to Le Chatelier's Principle, therefore, if heat is added, more product (NO2) will be produced, and equilibrium would shift towards the right side. This is choice 3.
Make an observation.
Conduct research.
Form hypothesis.
Test hypothesis.
Record data.
Draw conclusion.
Replicate.
One thing that is designed to change in the set up of the experiment. ( The things that I can change) Independent Variable.
The mole ratio is 4 NO2 to 3 O2; 4:3