# Acid-base related chemistry [closed]

What is the function of silica, $\ce{SiO2}$ in the equation $$\ce{CaO + SiO2 -> CaSiO3}$$ a) A basic oxide b) A acidic oxide c) A reducing agent d) An oxidising agent

Please explain.

• Please note that the homework policy on this site requires you to show some personal effort. – Klaus-Dieter Warzecha Mar 4 '15 at 4:54
• Consider to answer one... Way to go @KlausWarzecha! And, I wanna second his request Tanzeel, so I say: This is a homework question. We have a policy which states that ‎you should show your thoughts and\or efforts into solving the problem. It'll make us certain that ‎we aren't doing your homework for you. Otherwise, this question may get closed.‎ – M.A.R. Mar 4 '15 at 12:40

## 1 Answer

Since this sounds like a homework question, I will not provide a full solution!

### Is $\ce{SiO2}$ an oxidizing or reducing agent in the reaction?

Figure out the oxidation state for the $\ce{Ca}$ and $\ce{Si}$ in the starting materials and the product. As a rule of thumb, consider the oxidation state of (-2) for $\ce{O}$. Unless peroxides are concerned, this works well.

$$\ce{Ca^{(+2)}O + Si^{(+4)}O2 -> Ca^{(+2)}Si^{(+4)}O3}$$
Apparently, there is no change - this is not a redox reaction!

### Is $\ce{SiO2}$ a basic or an acidic oxide?

• How are basic and acidic oxides defined?
• Are there any rules (of thumb) for the oxides of metals and non-metals?

Metal oxides are usually basic oxides. These can be considered anhydrides of the corresponding metal hydroxides, $\ce{CaO}$ is a typical example: $\ce{CaO + H2O -> Ca(OH)2}$ What about $\ce{SiO2}$?