Question

Which of the following is a synthesis reaction?

C2H4 + 3O2 yields 2CO2 + 2H2O

2HBr yields H2 + Br2

CO2 + H2O yields H2CO3

F2 + 2 HCl yields Cl2 + 2HF

Answer 1

CO2 + H2O yields H2CO3 is a synthesis reaction.

Answer 2

Answer: The correct answer is $CO_2+H_2O\rightarrow H_2CO_3$

Explanation:

Synthesis reaction is defined as the reaction in which two or more small substances combine together to form a single large compound. General equation representing this reaction follows:

$A+B\rightarrow AB$

For the given reactions:

Reaction 1:  $C_2H_4+3O_2\rightarrow 2CO_2+2H_2O$

This reaction is considered as a combustion reaction because here, hydrocarbon is reacting with oxygen gas to produce carbon dioxide and water molecule.

Reaction 2:  $2HBr\rightarrow H_2+Br_2$

This reaction is considered as a decomposition reaction because here, one substance is forming two smaller substances.

Reaction 3: $CO_2+H_2O\rightarrow H_2CO_3$

This reaction is considered as a synthesis reaction because here, two smaller substances are forming one single compound.

Reaction 4:  $F_2+2HCl\rightarrow Cl_2+2HF$

This reaction is considered as a single displacement reaction because here, a more reactive element is displacing a less reactive element.

Hence, the correct answer is $CO_2+H_2O\rightarrow H_2CO_3$