RCl2+2KOH=R(OH)2+2KCl
RCl3+3KOH=R(OH)3+3KCl
Ta có nRCl2=nR(OH)2
mR(OH)2=19,8g => nR(OH)2= 19,8/(R+34) mol
mRCl= 0,5R => nRCl= 0,5R/(R+35,5)
=> Ta có pt 0,5R/(R+35,5)=19,8/(R+34)
<=> 0,5R(R+34)=19,8(R+35,5)
<=> 0,5R^2-2,8R-702,9=0
<=> R=40 => R là Ca ?????