Question

Calculate the amount of oxygen gas required and magnesium oxide formed when 60g of magnesium is burned completely in oxygen.

Answer 1

• The balanced chemical equation for the burning of magnesium is $2\mathrm{Mg}\left(\mathrm{s}\right)+{\mathrm{O}}_{2_{}}\left(\mathrm{g}\right)\to 2\mathrm{MgO}\left(\mathrm{g}\right)$
• We have to calculate the total mass of the product and reactant. to calculate it we have to know the individual mass of the element in the reaction. The atomic mass of magnesium is 24.3 and oxygen is 16.
• The mass equation of the reaction can be written as:
• $$\begin{gathered} 2\mathrm{x}24.3+2\mathrm{x}16\to 2(24.3+16) \\ 48.6\mathrm{g}+32\mathrm{g}\to 80.6\mathrm{g} \end{gathered}$$
• From the mass equation, it's clear that 48.6g of magnesium is reacting with 32g of oxygen to form 80.6g of magnesium oxide.
• So for 60g of magnesium, We need to calculate like this $$\begin{gathered} 48.6\mathrm{g}\to 32\mathrm{g} \\ 60\mathrm{g}\to \mathrm{xg} \end{gathered}$$ (cross multiplication done here to get the value of x) (x is the unknown amount of oxygen)
• $$\begin{gathered} 48.6\mathrm{X}\mathrm{x}=32\mathrm{X}60 \\ \mathrm{x}=(32\mathrm{X}60)/48.6 \\ =39.5\mathrm{g} \end{gathered}$$
• So, 39.5gm of oxygen gas is required.
• Similarly, the amount of magnesium oxide formed is $$\begin{gathered} 48.6\mathrm{g}\to 80.6\mathrm{g} \\ 60\mathrm{g}\to \mathrm{xg} \end{gathered}$$ (cross multiplication done here to get the value of x) (x is the unknown amount of magnesium oxide)
• $$\begin{gathered} 48.6\mathrm{X}\hspace{0.17em}\mathrm{x}=80.6\mathrm{X}60 \\ \mathrm{x}=(80.6\mathrm{X}60)/48.6 \\ =99.5\mathrm{g} \end{gathered}$$
• So, 99.5g of magnesium oxide is formed when 60g of magnesium and 39.5g of oxygen react together.