# Hydrofluoric acid (HF) reacts with silicon dioxide to produce silicon tetraflouride and water. How do you write the balanced equation for this reaction?

Dec 30, 2015

$4 {\text{HF"_text((aq]) + "SiO"_text(2(s]) -> "SiF"_text(4(g]) uarr + 2"H"_2"O}}_{\textrm{\left(l\right]}}$

#### Explanation:

Start by writing the chemical formulas of the reactants, which are

• hydrofluoric acid, $\text{HF}$
• silicon dioxide, ${\text{SiO}}_{2}$

Do the same for the products, which are

• silicon tetrafluoride, ${\text{SiF}}_{4}$
• water, $\text{H"_2"O}$

Before writing the unbalanced chemical equation for this reaction, it's important to note that this reaction is actually used to decorate glass by inducing etching patterns on it surface.

Aqueous hydrofluoric acid will react with the glass, which is represented by silicon dioxide, and produce silicon tetrafluoride, a gas that will be given off, and liquid water.

The unbalanced chemical equation will thus be

${\text{HF"_text((aq]) + "SiO"_text(2(s]) -> "SiF"_text(4(g]) uarr + "H"_2"O}}_{\textrm{\left(L\right]}}$

To balance this equation, all you have to do is multiply the hydrofluoric acid by $4$ and the water by $2$. This will ensure that all the atoms present on the reactants' side are accounted for on the products' side.

$4 {\text{HF"_text((aq]) + "SiO"_text(2(s]) -> "SiF"_text(4(g]) uarr + 2"H"_2"O}}_{\textrm{\left(l\right]}}$

I think that this reaction can also produce aqueous hexafluorosilicic acid, ${\text{H"_2"SiF}}_{6}$, and water.

Mind you, and this should go without saying, hydrofluoric acid is extremely, extremely dangerous! A lot of horrific injuries have occurred while using hydrofluoric acid for glass etching projects!

Here's a very cool video showing the reaction between a glass light bulb and hydrofluoric acid