Mg + 1/2O₂ ⇒ MgO
MMg=24g/mol
MMgO=AMg+AO=24+16=40g/mol
MO2=2AO=2*16=32g/mol
a) 24g Mg....................40g MgO
xg.................................1,2g MgO
x=24*1,2/40=0,72g Mg
b) n=m/M=0,72/24=0,03 moli Mg
c) 0,5*32g O₂..........................40g MgO
xg...............................................1,2g MgO
x=0,5*32*1,2/40=0,48g O₂
n=m/M=0,48/32=0,015 moli O₂