Question

Use the reaction given below to solve the problem that follows: Calculate the mass in grams of aluminum metal required to react with 115 g of oxygen gas.
4 Al + 3 O2 ——> 2 Al2O3

Answer: _____ grams Al

Answer 1

Answer:

129.4g

Explanation:

Reaction equation":

            4Al   + 3O₂  →  2Al₂O₃

Given mass of oxygen  = 115g

Unknown:

mass of aluminum metal that reacted;'

Solution:

We need to convert the given mass of O₂ to mole;

  Number of moles  = $\frac{mass}{molar mass}$

       Molar mass of O₂ = 2(16) = 32g/mol

    Number of moles  = $\frac{115}{32}$   = 3.6mol

From the balanced reaction equation:

  3 moles of O₂ reacted with 4 mole of Al

  3.6 moles of O₂ will react with $\frac{3.6 x 4}{3}$   = 4.8mol

Mass of Al  = number of moles x molar mass

Mass of Al  = 4.8 x 27  = 129.4g