Can someone pls help me with the top one?!

What does x represent in the formula for the compound xcl4?

Consider the reaction: n2(g) + o2(g) ⇄ 2no(g) kc = 0.10 at 2000oc starting with initial concentrations of 0.040 mol/l of n2 and 0.040 mol/l of o2, calculate the equilibrium concentration of no in mol/l how would this be done?

Consider the four elements above. which one of these elements will combine with oxygen in a 1: 1 ratio?