Underline the correct verb form. 1 Chinese is difficult to learn. 2 €100 was too much for the jacket. 3 Some children have very bad manners.

CaCO3 = CaO + CO2
CaO + 2H2O = Ca(OH)2
Ca(OH)2 + Na2CO3 = CaCO3 + 2NaOH
CaCO3 + CO2 +  H2O= Ca(HCO3)2 
Ca(HCO3)2 = CaCO3 + CO2 + H2O
2) C + O2 + CO2
2CO2 = 2CO + O2
2CO + O2 = 2CO2
CO2 + H2 = H2O + C