39)$\rm 2Na + 2H_2O \rightarrow 2NaOH + H_2$

40)$\rm 2K + 2H_2O \rightarrow 2KOH + H_2$

41)$\rm Ba + 2H_2O \rightarrow Ba(OH)_2 + H_2$

42)$\rm Ca + 2H_2O \rightarrow Ca(OH)_2 + H_2$

43) Không xảy ra.

44) Không xảy ra.

45)$\rm Cu(OH)_2$ `\overset(t^°)(->)` $\rm CuO + H_2O$

46)$\rm Fe(OH)_2$ `\overset(t^°)(->)` $\rm FeO + H_2O$

47)$\rm 2Fe(OH)_3$ `\overset(t^°)(->)` $\rm Fe_2O_3 + 3H_2O$

48)$\rm NaOH + HCl \rightarrow NaCl + H_2O$

Đáp án:

$\rm 39.\ Na+H_2O\to NaOH+\dfrac{1}{2}H_2\\40.\ K+H_2O\to KOH+\dfrac{1}{2}H_2\\41.\ Ba+2H_2O\to Ba(OH)_2+H_2\\42.\ Ca+2H_2O\to Ca (OH)_2+H_2\\43.\ 3Fe+4H_2O\xrightarrow{t^°<570^°C}Fe_3O_4+4H_2\\43'.\ Fe+H_2O\xrightarrow{t^°>570^°C}FeO+H_2$

$\rm 44.\ NaOH\not\to$

$\rm 45.\ Cu (OH)_2\xrightarrow{t^°}CuO+H_2O\\46.\ Fe(OH)_2\xrightarrow{t^°}FeO+H_2O\\47.\ 2Fe(OH)_3\xrightarrow{t^°}Fe_2O_3+3H_2O\\48.\ NaOH+HCl\to NaCl+H_2O$

43. Học sinh có thể chọn 1 trong 2 phương trình.