Hydrofluoric Acid + Silicon Dioxide Reaction Explained

[hola]

Gaseous hydrofluoric acid reacts with solid silicon dioxide.
My work (did a double replacement):
HF+SiO2------>H2O+SiF

But this doesn't look right. Why?
1. It looks weird.
2. How much valence electrons is Si supposed to have?
3. We're not dealing with solutions.


Anyone know the answer?

 

[Haxx0rm4ster]

ohhh man i do really bad in these. You pretty much have to memorize lots of rules.
I can answer #2 though, since O = -2 and the substance is a solid, then the compound is not an ion thus Si being 4+ . Or...just count from left to right in periodic table. Noting that Si was the cation.