1) Write the chemical equation.
[tex]P_4+O_2\rightarrow P_4O_{10}[/tex]2) List the elements in the reactants and in the products.
Reactants.
P: 4
O: 2
Products
P: 4
O: 10
Balance O.
[tex]P_4+5O_2\rightarrow P_4O_{10}[/tex]3) Moles of O2 needed.
The molar ratio between P4 and O2 is 1 mol P4: 5 mol O2.
[tex]mol\text{ }O_2=3.8\text{ }mol\text{ }P4*\frac{5\text{ }mol\text{ }O_2}{1\text{ }mol\text{ }P_4}=19\text{ }mol\text{ }O_2[/tex]If 3.8 mol P4 are used, 19 mol O2 are needed.
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