Answered

The equation for the decomposition of magnesium nitrate is shown:

[tex]\[2 \text{Mg}( \text{NO}_3)_2( s ) \rightarrow 2 \text{MgO}( s ) + 4 \text{NO}_2( g ) + \text{O}_2( g )\][/tex]

Which volume of gas is produced when 0.1 moles of magnesium nitrate is decomposed completely?

A. [tex]\(1.2 \, \text{dm}^3\)[/tex]

B. [tex]\(4.8 \, \text{dm}^3\)[/tex]

C. [tex]\(6.0 \, \text{dm}^3\)[/tex]

D. [tex]\(8.4 \, \text{dm}^3\)[/tex]



Answer :

To determine the volume of gas produced when 0.1 moles of magnesium nitrate (Mg(NO₃)₂) decomposes completely, we need to use the stoichiometry of the given chemical equation and the ideal gas law's approximation that 1 mole of any gas at standard temperature and pressure (STP) occupies 22.4 dm³.

1. Balanced Chemical Equation:
[tex]\[ 2 \, Mg(NO_3)_2(s) \rightarrow 2 \, MgO(s) + 4 \, NO_2(g) + O_2(g) \][/tex]

2. Determine the moles of gases produced:
- According to the balanced equation, 2 moles of Mg(NO₃)₂ produce 4 moles of NO₂ and 1 mole of O₂.
- Therefore, 1 mole of Mg(NO₃)₂ produces 2 moles of NO₂ and 0.5 mole of O₂.

3. For 0.1 moles of Mg(NO₃)₂:
- Moles of NO₂ produced: [tex]\(0.1 \, \text{moles of Mg(NO₃)₂} \times 2 \, \frac{\text{moles of NO₂}}{\text{moles of Mg(NO₃)₂}} = 0.2 \, \text{moles of NO₂}\)[/tex]
- Moles of O₂ produced: [tex]\(0.1 \, \text{moles of Mg(NO₃)₂} \times 0.5 \, \frac{\text{moles of O₂}}{\text{moles of Mg(NO₃)₂}} = 0.05 \, \text{moles of O₂}\)[/tex]

4. Total moles of gas produced:
[tex]\[ 0.2 \, \text{moles of NO₂} + 0.05 \, \text{moles of O₂} = 0.25 \, \text{moles of gas} \][/tex]

5. Volume of gas at STP:
- Given that 1 mole of any gas at STP occupies 22.4 dm³:
[tex]\[ \text{Volume of gas} = 0.25 \, \text{moles} \times 22.4 \, \frac{\text{dm}^3}{\text{mole}} = 5.6 \, \text{dm}^3 \][/tex]

Therefore, the volume of gas produced when 0.1 moles of magnesium nitrate decompose completely is:

[tex]\[ \boxed{5.6 \, \text{dm}^3} \][/tex]

Since none of the provided options match this volume exactly, it seems there was a mistake in the provided options. The correct volume should be [tex]\(5.6 \, \text{dm}^3\)[/tex].