Among the following how many are acidic oxides? MgO,  Al2O3,  CO2,   CO,   B2O3, Tl2O3, SnO2,  PbO2, K2OMgO,  Al2O3,  CO2,   CO,   B2O3, Tl2O3, SnO2,  PbO2, K2O

Acidic oxides, also known as acid anhydrides, are usually non-metal oxides. They react with water to form acids or with bases to form salts.

From the list provided, the acidic oxides are:

1. CO2 (Carbon Dioxide)
2. CO (Carbon Monoxide)
3. B2O3 (Boron Trioxide)
4. Tl2O3 (Thallium(III) Oxide)
5. SnO2 (Tin(IV) Oxide)
6. PbO2 (Lead(IV) Oxide)

So, there are 6 acidic oxides in the list provided.