The existence of isotopes violates one of the original ideas of dalton's atomic theory. which one?

Explanation:

One of the Dalton's postulates states that:

The atoms of same element are similar in the shape and the mass and other properties but different from atoms of other elements.

But the existence of isotopes violates this postulate because isotopes are the species which have same atomic number but different atomic mass. For example, carbon exist in three isotopes which are C-12, C-13 and C-14 and have different mass and some properties and is a contradiction of this postulate.

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