Потому что в таблице Менделеева так написано.
CaSIO3+HCl=CaCl2+H2SiO3
Ca(OH)2+FeCl2=CaCl2+Fe(OH)2
S+O2=SO2
H2SO3=H2O+SO2
только по 2 примера, просто больше в голову не лезет...
а)<span>2Ca + O2 = 2CaO</span>
<span>б)<span>2Na + 2H2O = 2NaOH + H2</span></span>
<span><span>в)<span>Cu(OH)2 = CuO + H2O</span></span></span>
<span><span><span>г)<span>2LiOH = Li2O + H2O</span></span></span></span>
<span><span><span><span>д)<span>Mg + H2SO4 = MgSO4 + H2</span></span></span></span></span>
<span><span><span><span><span>е)<span>Zn + CuSO4 = ZnSO4 + Cu</span></span></span></span></span></span>
<span><span><span><span><span><span>ж)-</span></span></span></span></span></span>