Question

How much magnesium must be burnt in oxygen to obtain 1kg of magnesium oxide

Answer 1

1. The reaction of burning of Magnesium in presence of Oxygen to give Magnesium Oxide is as follows:

2 Mg(s) + O₂(g) $\to$ 2 MgO (s)

2. 2 moles of Mg give 2 moles of MgO.

Number of moles in 1kg of MgO = $\frac{Givenmass}{Molarmass}=\frac{1000}{40.3}=24.8moles(1kg=1000g)$

3. So, 24.8 moles of Mg is required.

So mass of Mg in 24.8 moles = $$\begin{gathered} Numberofmoles\times Molarmass \\ =24.3\times 24.3=590g=0.59g \end{gathered}$$