Total number of acidic oxides among N2O3,NO2, N2O,Cl2O7,SO2,CO,CaO,Na2O and NO is _____ .

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

1. N2O3: Nitrogen is a non-metal. So, N2O3 is an acidic oxide.
2. NO2: Nitrogen is a non-metal. So, NO2 is an acidic oxide.
3. N2O: Nitrogen is a non-metal. However, N2O does not react with water to form an acid. So, N2O is not an acidic oxide.
4. Cl2O7: Chlorine is a non-metal. So, Cl2O7 is an acidic oxide.
5. SO2: Sulfur is a non-metal. So, SO2 is an acidic oxide.
6. CO: Carbon is a non-metal. So, CO is an acidic oxide.
7. CaO: Calcium is a metal. So, CaO is not an acidic oxide. It is a basic oxide.
8. Na2O: Sodium is a metal. So, Na2O is not an acidic oxide. It is a basic oxide.
9. NO: Nitrogen is a non-metal. So, NO is an acidic oxide.

Therefore, the total number of acidic oxides among N2O3, NO2, N2O, Cl2O7, SO2, CO, CaO, Na2O and NO is 6.