a, Các PTHH:
$2K+2H_2O\to 2KOH+H_2\uparrow$
$K_2O+H_2O\to 2KOH\ \ (*)$
$n_{H_2}=\dfrac{2,24}{22,4}=0,1\ (mol)$
Theo phương trình:
$n_K=n_{KOH}=2n_{H_2}=2.0,1=0,2\ (mol)$
$\to m_K=0,2.39=7,8\ (g)$
$\to m_{K_2O}=26,6-7,8=18,8\ (g)$
$\to n_{K_2O}=\dfrac{18,8}{94}=0,2\ (mol)$
Theo phương trình $(*):$
$n_{KOH}=2n_{K_2O}=0,2.2=0,4\ (mol)$
$\to m_{KOH}=56.(0,2+0,4)=33,6\ (g)$