Answer to Question #113911 in General Chemistry for mrs

Question

Calculate the mass of oxygen that reacted with the magnesium
mass of crucible, lid and contents after reaction – mass of crucible + lid + magnesium

Answer 1

Magnesium reacts with oxygen to produce magnesium oxide:

2Mg(s) + O₂(g) ----> 2MgO(s)

Number of moles of Mg = mass(Mg) / M_r(Mg) = mass(Mg) / 24.3

Looking at the balanced chemical equation, 2 mol of Mg reacts with 1 mol of O₂, so n mol of Mg reacts with n/2 mol of O₂

mass of O₂ = M_r × number of moles of O₂ = 32.0 x n/2