Wood sinks in ethanol => wood has higher density than ethanol.
wood floats in gasoline=> wood has lower density than gasoline
N₂O₄ (g) ⇌ 2 NO₂ (g)
Kc = [ NO₂ ]² / [ N₂O₄ ]
4.2 = [ 0.785 ] [ N₂O₄ ]
[ N₂O₄ ] = 4.2 / 0.785
[N₂O₄ ] = 5.350 M
hope this helps!
