Calculate the number of atoms/molecules present in (a) 1 mole of sulphur.
(b) 2 moles of oxygen gas.

1 mole contains 6.02 ×10^23 atoms

1 mole of Sulphur will contain 6.02 ×10^23 atoms

2moles of. Oxygen will contain 2 x 6.02×10^23 atoms. This gives 12.04 × 10^23 atoms

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