MCH4=16g/mol
n=m/M=192/16=12 moli CH4
x..........x...............x...........x
a) CH4 + Cl2 => CH3Cl + HCl
y.............2y...............y.............2y
CH4 + 2Cl2 => CH2Cl2 + 2HCl
z..............3z............z.............3z
CH4 + 3Cl2 => CHCl3 + 3HCl
w...............w
CH4 => CH4
b) x/y=2/2 => y=2x/2
x/z=2/1 => z=x/2
x/w=2/1 => w=x/2
x+y+z+w=12 => x+2x/2+x/2+x/2=12 => 6x/2=12 => x=4 moli
y=4 moli
z=2 moli
w=2 moli
m CHCl3= 2*119,5=239g
b) x+2y+3z=4+2*4+3*2=18 moli HCl
Cm=n/Vs=>Vs=n/Cm=18/0,2=90L HCl