How many grams of hydrogen gas (2.016 g/mol) can be produced when 28.56 g of aluminum (26.98 g/mol) are reacted?

Mass of Hydrogen gas produced : 3.202 g

A reaction coefficient is a number in the chemical formula of a substance involved in the reaction equation. The reaction coefficient is useful for equalizing reagents and products.

Hydrogen gas can be obtained by reacting metals with acids

Reaction of Aluminium(Al) and  Hydrochloric acid(HCl)

2Al + 6HCl → 2AlCl₃ + 3H₂

mass of Aluminium : 28.56 g, so mol Al :

From equation, mol ratio of Al : H₂ = 2 : 3, so mol H₂ :

Mass of Hydrogen gas produced :

the correct answer is:

a. formation of precipitation