“Explosive silane gas” experiment

How to obtain a gas that sparks and pops

Stand­ing ova­tions are doubt­less a per­former’s best re­ward. But for chemists, the sub­stances that they work with can pro­vide all the ap­plause they need! In this ex­per­i­ment, we’ll make silane gas, which makes a clap­ping sound.

Safe­ty pre­cau­tions

  • Wear pro­tec­tive gloves, glass­es, and a mask.

  • Per­form this ex­per­i­ment in a well-ven­ti­lat­ed room.

  • Ob­serve safe­ty rules when work­ing with heat­ing de­vices and com­bustible mix­tures.

Warn­ing! Don’t try to re­peat this ex­per­i­ment with­out a pro­fes­sion­al su­per­vi­sion!

Reagents and equip­ment:

  • 50 mL 10% sul­fu­ric acid so­lu­tion;
  • 3 g dry sil­i­con diox­ide;
  • 6 g mag­ne­sium pow­der;
  • gas burn­er;
  • test tube;
  • stand;
  • Petri dish;
  • beaker.

Step-by-step in­struc­tions

Heat­ed sil­i­con diox­ide is mixed with mag­ne­sium pow­der in a 1:2 ra­tio. The mix­ture is then added to a test tube (the test tube must be held with the neck fac­ing away!), and heat­ed with a gas burn­er. Di­lut­ed sul­fu­ric acid is poured into a Petri dish, and the cooled pow­der is added to it.

Pro­cess­es de­scrip­tion

When the mix­ture of sil­i­con diox­ide and mag­ne­sium pow­der is heat­ed, two pro­cess­es take place at once.

The re­duc­tion of sil­i­con from ox­ide:

SiO₂ + 2Mg = Si + 2MgO

And the re­ac­tion of sil­i­con with mag­ne­sium, with the for­ma­tion of mag­ne­sium sili­cide:

Si + 2Mg = Mg₂Si

Mag­ne­sium sili­cide is hy­drolyzed in the sul­fu­ric acid so­lu­tion, and silane gas is re­leased. It self-com­busts in air.

Mg₂Si + 2H₂­SO₄ = 2Mg­SO₄ + SiH₄

SiH₄ + 2O₂ = SiO₂ + 2H₂O