Answer: 16.32 g of 
as excess reagent are left.
Explanation:
To calculate the moles :
According to stoichiometry :
2 moles of 
require = 1 mole of
Thus 0.34 moles of will require=
of
Thus is the limiting reagent as it limits the formation of product and is the excess reagent.
Moles of left = (0.68-0.17) mol = 0.51 mol
Mass of 
Thus 16.32 g of as excess reagent are left.
umm how do you begin answering that ??
Answer:
alkali metals
Explanation:
they all react vigorously or even explosively with cold water, resulting in the displacement of hydrogen.
Molecular mass of H2O is: 16+2*1=18
so moles of 40g of H2O is: 40/18=2.22
