Ca + O → A––
Ca + N2 → B––. A & B are
CaO, Ca3 N2
CaO2, Ca3N2
CaO, CaN2
CaO, CaN3
Ca + O → CaO
6Ca + 2N2 → 2Ca3N2
Identify the correct order of acidic strength of CO2, CuO, CaO, and H2O: