1)2Ca+O2===>2CaO
2)CaO+CO2===>CaCO3
3)CaCO3+2HCl===><span>CaCl2+H2O+CO2</span>
<span>4)CaCl2+2HNO3===>Ca(NO3)2+2HCl</span>
2Ca + O2 = 2CaO