Greatest average number of neutrons out of tin antimony tellurium iodine?

Iodine has the greatest average number of neutrons.  

Step-by-step explanation:

Tin

Tin has 41 isotopes with every mass number from 99 to 139. Thus, the average mass number is 119.

Tin has atomic number 50, so the average number of neutrons

is 119 – 50 = 69.

Antimony

Antimony has 37 isotopes with every mass number from 103 to 139. Thus, the average mass number is 121.

Antimony has atomic number 51, so the average number of neutrons

is 121 – 51 = 70.

Tellurium

Tellurium has 39 isotopes with every mass number from 104 to 142. Thus, the average mass number is 123.

Tellurium has atomic number 52, so the average number of neutrons

is 123 – 52 = 71.

Iodine

Iodine has 37 isotopes with every mass number from 108 to 144. Thus, the average mass number is 126.

Iodine has atomic number 53, so the average number of neutrons

is 126 – 53 = 73.

Iodine has the greatest average number of neutrons.  

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