Question

Disilane(Si2H6 ) is a gas that reacts with oxygen to give silica(SiO2 ) and water. Calculate mass of silica that would form if 100 cm3 Disilane (with a density 2.48 × 10–3 gm cm–3) reacted with excess oxygen.

Answer 1

Given:

Volume of disilane = 100cm³

Density of disilane = 2.48 × 10⁻³ gm cm⁻³

To find:

Mass of silica

Solution:

Mass of disilane can be calculated by the formula-

          $Density = \frac{Mass}{Volume}$

here, density = 2.48×10⁻³ gcm³

        Volume = 100 cm³

Therefore, the mass of disilane is -

      mass = density × volume

                 = 2.48 × 10⁻³ × 100

                = 0.248 g

To calculate moles of disilane we have,

       $moles = \frac{mass}{molar mass }$

Molar mass of disilane = 62.22 gmol⁻¹

Therefore,  $moles = \frac{0.248}{62.22}$

                  moles of disilane = 0.004 mol

Now, disilane gas reacted with oxygen and forms silica and water. the balanced chemical reaction involved is-

   2Si₂H₆ + 7O₂ →  4SiO₂ + 6H₂O

According to stoichiometry,

2 moles of disilane forms = 4 moles of SiO₂

0.004 moles of disilane forms = $\frac{4}{2} \times 0.004$ moles of SiO₂

                                                   = 0.008 moles of SiO₂

 Therefore, mass of silica will be calculated as-

    mass = moles × molar mass of silica

     mass = 0.008 moles × 60.08 gmol⁻¹

    mass = 0.4806 g

So, the mass of silica is 0.4806g