# Question #60406

Feb 27, 2015

At room temperature, magnesium reacts very slowly with water; to speed up the reaction, magnesium is made to react with water vapor to form magnesium hydroxide and hydrogen gas by heating the sample

$2 {H}_{2} {O}_{\left(g\right)} + M {g}_{\left(s\right)} \to M g {\left(O H\right)}_{2} \left(a q\right) + {H}_{2} \left(g\right)$

Here's a video of that reaction:

Chlorine reacts with water to produce a mixture of hypochlorous acid and hydrochloric acid

$C {l}_{2 \left(g\right)} + {H}_{2} {O}_{\left(l\right)} \to H C {l}_{\left(a q\right)} + H O C {l}_{\left(a q\right)}$

The hypochlorous acid will decompose when exposed to sunlight to form hydrochloric acid and oxygen gas

$2 H O C {l}_{\left(a q\right)} \to 2 H C {l}_{\left(a q\right)} + {O}_{2 \left(g\right)}$

Finally, silicon can't react with water in free form because you just can't find silicon in free form in nature. There are however a number of silicon compounds that can react with water; for example, silicon dioxide, or silica, reacts with water at high temperatures to form monosilicic acid, $S i {\left(O H\right)}_{4}$ - you'll sometimes see this written as ${H}_{4} S i {O}_{4}$

$S i {O}_{2 \left(s\right)} + 2 {H}_{2} {O}_{\left(l\right)} \to S i {\left(O H\right)}_{4 \left(s\right)}$