Câu 1:
$n_{CO_2}=\dfrac{8,96}{22,4}=0,4(mol)$
$CO_2+Ca(OH)_2\to CaCO_3+H_2O$
$\Rightarrow n_{CaCO_3}=0,4(mol)$
$\Rightarrow m=0,4.100=40g$
$\to B$
Câu 2:
$Na_2O+H_2O\to 2NaOH$
$NaOH$ là kiềm.
$\to D$
Câu 3:
$n_{H_2}=0,225(mol)$
$Al+NaOH+H_2O\to NaAlO_2+1,5H_2$
$\Rightarrow n_{Al}=0,15(mol)$
$\to m=0,15.27=4,05g$
$\to B$