Which of the following is a synthesis reaction?
C2H4 + 3 O2 yields 2 CO2 + 2 H2O
2HBr yields H2 + Br2
CO2 + H2O yields H2CO3
F2 + 2 HCl yields Cl2 + 2 HF
C2H4 + 3 O2 yields 2 CO2 + 2 H2O
2HBr yields H2 + Br2
CO2 + H2O yields H2CO3
F2 + 2 HCl yields Cl2 + 2 HF