Question

If you have 15.0 g of Na, how many grams of O2 are required for the reactionSodium reacts with oxygen to produce sodium oxide.4Na(s)+O2(g)→2Na2O(s)

Answer 1

$4Na_{(s)}+O_2\rightarrow2Na_2O_{(s)}$

Firstly we convert the mass of Na to moles of Na:

$\begin{gathered} _nNa_{(s)}=\frac{mass}{molar\text{ }mass} \\ _nNa_{(s)}=\frac{15.0g}{14\text{ }gmol^{-1}} \\ _nNa_{(s)}=1.07\text{ }mole \end{gathered}$

Based on the mole ratio 4 moles of Na reacts with 1 mole of O2. Therefore 1.07 mole of Na would react with x mole of oxygen gas. We determine x by:

$\begin{gathered} _nO_{2(g)}=1.07\text{ }mole\div4 \\ _nO_{2(g)}=0.27\text{ }mole \end{gathered}$

We will now convert 0.27mol of oxygen gas to mass of oxygen gas:

$\begin{gathered} mass=mole\times molar\text{ }mass \\ mass=0.27\times32\text{ }gmol^{-1} \\ mass=8.64g \end{gathered}$

Mass of O2 is 8.64g