What is the mass number of an atom containing 4 protons and 5 neutrons? How many total electrons would that neutral atom contain?
What is the element?
Will this element gain or lose electrons?
How many total electrons would an ion of that element have?
What is the charge on that ion (ex. +1, -1, +2, -2, etc.)?
Is this ion an anion or cation?
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What other element has the same number of electrons as the ion you have identified?

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