$PTK_{Na_2SO_4}=23.2+32+16.4=142 (đvC)$
$PTK_{Al_2(SO_4)_3}=27.2+(32+16.4).3=342 (đvC)$
$PTK_{Fe_2(SO_4)_3}=56.2+(32+16.4).3=400 (đvC)$
$PTK_{CuSO_4}=64+32+16.4=160 (đvC)$
$PTK_{Al_2O_3}=27.2+16.3=102 (đvC)$
---------------------Nguyễn Hoạt-------------------