45% din 8 = 45*8/100=3,6moli CH4
2:1 => 2x moli mono si x moli dicloro
1mol...1mol..1mol......1mol
CH4 + Cl2 -> CH3-Cl + HCl
2x.......2x.......2x...........2x
1mol...2moli...1mol........2moli
CH4 + 2Cl2 -> CH2Cl2 + 2HCl
x..........2x........x...............2x
1mol...1mol
CH4 -> CH4
4,4moli..4,4moli
3x=3,6 => x=1,2moli
avem si 1,2*4=4,8moli Cl2 consumati => 0,2moli ramasi in amestecul gazos
amestecul gazos final=7x+4,4+0,2=7*1,2+4,4+0,2=13moli
%clorurametil=2x*100/13=2,4*100/13=18,46% => A)