[vanderwaals]

Elemental silicon is oxidized by O2 to give a compound
which dissolves in molten Na₂CO₃. When this solution is
treated with aqueous hydrochloric acid, a precipitate
forms. What is the precipitate?
(A) SiH₄ (B) SiCO₃ (C) SiO₂ (D) SiCl₄

The answer is (C). I'm just very confused about what happens here. I thought that after elemental silicon is oxidized (the first step), SiO₂ would be produced...but I have no idea if that's correct. I don't know what the reaction with HCl has to do with anything either. Could someone guide me through what happens after each reaction? Thanks in advance!

[thetada]

What effect do you think the hydrochloric acid might have on the sodium carbonate?

[vanderwaals]

Well it reacts to form water and carbon dioxide...but I'm not sure how this is related to the precipitate

[AWK]

to give a compound
which dissolves in molten Na2CO3

This is chemical reaction.
See wikipedia: sodium silicate.

[thetada]

Well it reacts to form water and carbon dioxide...but I'm not sure how this is related to the precipitate

Turns out nothing but it doesn't hurt to consider all possibilities. The question is very misleadingly phrased, it's not dissolving to make a solution, it's reacting to make a new species.