What volume of oxygen is needed for the complete combustion of
\(\text{5}\) \(\text{g}\) of magnesium to form magnesium oxide?
The balanced equation for this reaction is:
\[2\text{Mg (s)} + \text{O}_{2}\text{(g)} \rightarrow 2\text{MgO(s)}\]
The number of moles of magnesium used is:
\begin{align*}
n &= \frac{m}{M}\\
& = \frac{\text{5}}{\text{24,3}}\\
& = \text{0,2058}\text{ mol}
\end{align*}
The mole ratio of \(\text{Mg}\) to \(\text{O}_{2}\) is \(2:1\). So
the number of moles of \(\text{O}_{2}\) is:
\begin{align*}
n_{\text{O}_{2}} & = n_{\text{Mg}} \times \frac{
\text{stoichiometric coefficient O}_{2}}{
\text{stoichiometric coefficient Mg}}\\
& = \text{0,2058}\text{ mol } \text{Mg} \times \frac{\text{1}\text{
mol } \text{O}_{2}}{\text{2}\text{ mol} \text{ Mg}}\\
& = \text{0,1029}\text{ mol } \text{O}_{2}
\end{align*}
The volume of oxygen is:
\begin{align*}
V & = (\text{22,4})n\\
& = (\text{22,4})(\text{0,1029})\\
& = \text{2,30}\text{ dm$^{3}$}
\end{align*}
Annalize is making a mini volcano for her science project. She mixes
baking soda (mostly \(\text{NaHCO}_{3}\)) and vinegar (mostly
\(\text{CH}_{3}\text{COOH}\)) together to make her volcano
erupt. The reaction for this equation is:
\[\text{NaHCO}_{3}\text{(s)} + \text{CH}_{3}\text{COOH(aq)}
\rightarrow \text{CH}_{3}\text{COONa(aq)} +
\text{H}_{2}\text{O(ℓ)} + \text{CO}_{2}\text{(g)}\]
What volume of carbon dioxide is produced if Annalize uses
\(\text{50}\) \(\text{ml}\) of \(\text{0,2}\)
\(\text{mol·dm$^{3}$}\) acetic acid?
The number of moles of acetic acid used is:
\begin{align*}
c &= \frac{n}{V}\\
\text{0,2}\text{ mol·dm$^{-3}$} & = \frac{n}{\text{0,05}\text{
dm$^{3}$}}\\
n & = \text{0,01}\text{ mol}
\end{align*}
The mole ratio of \(\text{CH}_{3}\text{COOH}\) to \(\text{CO}_{2}\)
is \(1:1\). So the number of moles of \(\text{CO}_{2}\) is
\(\text{0,01}\) \(\text{mol}\).
\begin{align*}
V & = (\text{22,4})n\\
& = (\text{22,4})(\text{0,01})\\
& = \text{0,224}\text{ dm$^{3}$}
\end{align*}
