Balancing chemical equations - 1 | Chemical Reactivity

2 C₈H₁₈ (l) + 25 O₂ (g) →  16 CO₂ (g) + 18 H₂O (l)
 

According to the stoechiometry of the balanced equation:
$\frac{{\mathrm{n}}_{\mathrm{C}8\mathrm{H}18}}{2}$ = $\frac{{\mathrm{n}}_{\mathrm{O}2}}{25}$  ⇒ $\frac{{\mathrm{m}}_{\mathrm{O}2}}{{\mathrm{M}}_{\mathrm{O}2}}$ = $\frac{25}{2}$ x $\frac{{\mathrm{m}}_{\mathrm{C}8\mathrm{H}18}}{{\mathrm{M}}_{\mathrm{C}8\mathrm{H}18}}$

m_O2 = 178 g
 

$\frac{{\mathrm{n}}_{\mathrm{C}8\mathrm{H}18}}{2}$ = $\frac{{\mathrm{n}}_{\mathrm{H}2\mathrm{O}}}{18}$ ⇒  n_H2O = $\frac{18}{2}$ x $\frac{{\mathrm{m}}_{\mathrm{C}8\mathrm{H}18}}{{\mathrm{M}}_{\mathrm{C}8\mathrm{H}18}}$
n_H2O = 4.01 mol