The speed of sound at

is approximately v=343 m/s. The distance covered by the sound wave is

And the time it takes is

Now we want to find how far the light travels during this time. Light travels at speed

, therefore the distance it covers during this time is
What if when I find my product, I get the same compound as I did in my
reactant? For example, FeCl3 + HCl ->FeCl3 + HCl. Then something is
wrong. In this case, FeCl3 and HCl usually don't react. In very
concentrated solutions of HCl, the FeCl4^- or FeCl6^-3 ion can form.
In... There you go my friend