When comparing be2 and h2:

i. be2 is more stable because it contains both bonding and antibonding valence electrons.
ii. h2 has a higher bond order than be2.
iii. h2 is more stable because it only contains 1s electrons.
iv. h2 is more stable because it is diamagnetic, whereas be2 is paramagnetic.

II

Explanation:

H2 has a bond energy of 1 while Be2 has a bond energy of zero. Be2 has 8 electrons which occupy four orbitals. Two of them are bonding molecuar molecular orbitals and the other two are antibonding molecular orbitals. The molecule is thus unstable. H2 has only two electrons which occupy the sigma 1s bonding molecular orbital having a bond order of 1. Hence it is a stable molecule.

as given the equation is

2al + 6 hcl > 2 alcl3 + 3 h2(g)

as per equation two moles of aluminum reacts with six moles of hcl to give two moles of alcl3 and three moles of hydrogen gas

given: three moles of al are present and 7 moles of hcl

for three moles of aluminum nine moles of hcl will be required

however as 7 moles of hcl are present so the limiting reagent is hcl

hcl is going to decide the number of moles of product formed

when six moles of hcl are present = 3 moles of h2 are formed

when one mole of hcl is present == 3/6 mole sof h2 will be formed

when 7 moles of hcl are present = 3 x 7/ 6 moles of h2 will be formed = 3.5 moles of h2