2.1 The reaction of nitrogendioxide and carbonmonoxide in the gas state to form carbondioxide and nitricoxide is represented by the equation on the figure: What are solutions of questions on the figure?

The reaction between nitrogen dioxide and carbon monoxide is

NO2(g)+CO(g)→NO(g)+CO2(g)

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.