+21 Sc, n = 45-21 = 24
Ответ: 24
1. 2Ca + O2 = 2CaO
2. CaO + H2O = Ca(OH)2
3. Ca(OH)2 + 2HNO3 = Ca(NO3)2 + 2H2O
1. 2Mg + O2 = 2MgO
2. MgO + 2HCl = MgCl2 + H2O
3. MgCl2 + 2LiOH = Mg(OH)2 + 2LiCl
Mg[2+] + 2Cl[-] + 2Li[+] + 2OH[-] = Mg(OH)2 + 2Li[+] + 2Cl[-]
Mg[2+] + 2OH[-] = Mg(OH)2
4. Mg(OH)2 + HNO3 = Mg(NO3)2 + H2O
Дано
m(Ca) = 20 g/mol
-----------------------
m(O2) -?
n(O2) = ?
2Ca+O2-->2CaO
M(Ca) = 40 g/mol
n(Ca) = m/M = 20/40 = 0,5 mol
2n(Ca) = n(O2) , n(O2) = 0.5/2 = 0.25 mol
M(O2) = 32 g/mol
m(O2) = n*M = 0.25 * 32 = 8 g
ответ 8г , 0.25 моль
<span>формула сполуки плюмбум (IV) оксиду--- </span>Pb(OH)4